JAVA Basic Shopping Cart Program

Question

I'm trying to create a simple shopping cart application. The problem is with the totalPrice that is displayed in the end (startScanning() method). I'm trying to to make the user input one of the four items as many times as they want(thus the do-while loop) and through the startScanning method, I am trying to figure out the number of times the user entered that item and thus later on calculating the totalPrice. Also the processItem method is used to give discount and tax based on items. Can you help me correct the for loops for the startScanning method in order to display the correct totalPrice?

import javax.swing.JOptionPane;

public class Shopping {
    static String itemScan;
    static String firstName; 
    static String surName;
    static int age;
    static double priceBanana = 0.75;
    static double priceApple = 0.75;
    static double priceMilk = 1.25;
    static double priceOrange = 1.50;
    public static String printWelcomeMessage () {
        firstName = JOptionPane.showInputDialog("Enter your name:");
        surName = JOptionPane.showInputDialog("Enter your surname:");
        String sAge = JOptionPane.showInputDialog("Enter your age:");
        age = Integer.parseInt(sAge);
            do {
            itemScan = JOptionPane.showInputDialog(surName + ", " + firstName + "("+age+"). Welcome to our supermarket! Start Scanning items. To stop, enter \'EXIT\'");
            }
        while (!itemScan.equalsIgnoreCase("Exit"));
            return itemScan;
    }
    public static double startScanning() {
        double newpriceBanana = 0;
        double newpriceMilk = 0;
        double newpriceApple = 0;
        double newpriceOrange = 0;
            for (int i = 0; itemScan.equalsIgnoreCase("Banana"); i++ ) {
                newpriceBanana = i*priceBanana;
            }
            for (int i = 0; itemScan.equalsIgnoreCase("Apple"); i++) {
                newpriceApple = i*priceApple;

            }
            for (int i = 0; itemScan.equalsIgnoreCase("Milk"); i++) {
                newpriceMilk = i*priceMilk;

            }
            for (int i = 0; itemScan.equalsIgnoreCase("Orange Juice"); i++) {
                newpriceOrange = i*priceOrange;
                } 


        double totalPrice = newpriceBanana + newpriceApple + newpriceMilk + newpriceOrange;
        return totalPrice;
    }
    public static void processItem() {
        // Note: I haven't considered orange juice as a fruit but a drink like milk.
        // Thus, no discount for orange juice.
        if (itemScan.equalsIgnoreCase("Apple") || itemScan.equalsIgnoreCase("Banana")) {
            priceBanana = priceBanana- (0.1*priceBanana);
            priceApple = priceApple- (0.1*priceApple);
        }
        else {
            priceMilk = priceMilk + (0.2*priceMilk);
            priceOrange = priceOrange + (0.2*priceOrange);
        }

    }

    public static String printReceipt() {
        String cardNumber = JOptionPane.showInputDialog("Please enter your 16-digit Credit Card Number:");
        int cardNum = Integer.parseInt(cardNumber.substring(12,16));
        String information =  "Printing Receipt...\n"+"Credit Card Number ends in: "+ cardNum + "\nTotal Amount: $"+ startScanning();

        return information;
    }
    public static void main(String[] args) {
    printWelcomeMessage();
    processItem();
    startScanning();
    JOptionPane.showMessageDialog(null, printReceipt());

    }
}