Easy cash register program help!

[Live01]

I've recently began learning java in my grade 11 computer course, and we recently recieved an assignment in which you must have the user enter a purchase amount, calculate pst and gst, output the total, calculate change from an inputted tender amount, and output the coin denominations required in 20s 10s 5s toonies loonies quarters dimes nickels and cents.

I have the program fully written, and it works. The problem is, the program is inaccurate by 1 cent. For example, I enter 10.00 as raw test data. the program calculate 8% tax and calculates 11.3, which is then formatted to show $11.30. I enter 20.00 as tender, and the program calculates change at 8.7 (formatted to show $8.70). Next, i multiply the change by 100 to get an exact amount of change in pennies. Here's the problem, 8.7 * 100 gets me an answer of 869 pennies, instead of 870.

I am using integer and modulus division as required. I can't figure this one out, can anyone help me out? Here's the source code:

import java.text.*;
public class CashRegister
{
public static void main (String [] args)
{
//Create a number format object to be used
NumberFormat nfc = NumberFormat.getCurrencyInstance();

//Declare and initialize variables
double purchase = 0.0;
double total = 0.0;
double change = 0.0;
double gst = 0.0;
double pst = 0.0;
double tender = 0.0;
int fullchange, changeleft = 0;
int twenties, tens, fives, toonies, loonies, quarters, dimes, nickels, pennies = 0;


//Declare and initilize constants
final double GSTRATE = 0.05; //Assigns 5% as gst rate
final double PSTRATE = 0.08; //Assigns 8% as pst rate

//Introduce the program to th user and tell the user how to use the program
System.out.println("\tWelcome to the Cash Register. Please follow the instructions.");

System.out.println(""); //inputs a blank line as a spacer

//Prompt the user for purchase amount
System.out.print("Please enter the purchase amount, before taxes ($0.00): $");
purchase = In.getDouble();

System.out.println(""); //inputs a blank line as a spacer

//Calculate gst and pst
gst = purchase * GSTRATE;
pst = purchase * PSTRATE;

//Calculate total
total = purchase + gst + pst;
System.out.println("unformatted total is: " + total); //DEBUGGING

//Print total to user
System.out.println("The total amount after taxes is: " + nfc.format(total));

System.out.println(""); //inputs a blank line as a spacer

//Prompt the user for tender amount
System.out.print("Please enter the tendered amount ($0.00): $");
tender = In.getDouble();

//Calculate change
change = tender - total;
System.out.println("change after calculation is: " + change);

//Output change and add a spacer
System.out.println("The total change from purchase is: " + nfc.format(change));
System.out.println(""); //inputs a blank line as a spacer

//Convert change to an integer (change amount in pennies)
changeleft = (int)(change * 100.0);
System.out.println("fullchange in pennies is: " + changeleft); //DEBUGGING

//Calculate coin denomination
twenties = changeleft / 2000;
changeleft = changeleft % 2000;
System.out.println("fullchange is: " + changeleft); //DEBUGGING
tens = changeleft / 1000;
changeleft = changeleft % 1000;
System.out.println("fullchange is: " + changeleft); //DEBUGGING
fives = changeleft / 500;
changeleft = changeleft % 500;
System.out.println("fullchange is: " + changeleft);
toonies = changeleft / 200;
changeleft = changeleft % 200;
System.out.println("fullchange is: " + changeleft);
loonies = changeleft / 100;
changeleft = changeleft % 100;
System.out.println("fullchange is: " + changeleft);
quarters = changeleft / 25;
changeleft = changeleft % 25;
System.out.println("fullchange is: " + changeleft);
dimes = changeleft / 10;
changeleft = changeleft % 10;
System.out.println("fullchange is: " + changeleft);
nickels = changeleft / 5;
changeleft = changeleft % 5;
System.out.println("fullchange is: " + changeleft);
pennies = changeleft;
System.out.println("fullchange is: " + changeleft);

//Output coin denomination
System.out.println("Please give the customer the following change:");
System.out.println("Twenties:\t\t" + twenties);
System.out.println("Tens:\t\t\t" + tens);
System.out.println("Fives:\t\t\t" + fives);
System.out.println("Toonies:\t\t" + toonies);
System.out.println("Loonies:\t\t" + loonies);
System.out.println("Quarters:\t\t" + quarters);
System.out.println("Dimes:\t\t\t" + dimes);
System.out.println("Nickels:\t\t" + nickels);
System.out.println("Pennies:\t\t" + pennies);

System.out.println(""); //Inputs a blank line as a spacer

//Output bill of sale
System.out.println("Purchase amount: " + nfc.format(purchase));
System.out.println("Gst tax amount: " + nfc.format(gst));
System.out.println("Pst tax amount: " + nfc.format(pst));
System.out.println("Total amount: " + nfc.format(total));
System.out.println("Tender recieved: " + nfc.format(tender));
System.out.println("Change amount: " + nfc.format(change));


} //End of main method
}//End of class