Javascript oop cashregister

function StaffMember(name,discountPercent){
    this.name = name;
    this.discountPercent = discountPercent;
}

var sally = new StaffMember("Sally", 5);
var bob = new StaffMember("Bob", 10);

// Create yourself again as 'me' with a staff discount of 20%
var me = new StaffMember("Eleison", 20);

var cashRegister = {
    total:0,
    lastTransactionAmount: 0,
    add: function(itemCost){
        this.total += (itemCost || 0);
        this.lastTransactionAmount = itemCost;
    },
    scan: function(item,quantity){
        switch (item){
        case "eggs": this.add(0.98 * quantity); break;
        case "milk": this.add(1.23 * quantity); break;
        case "magazine": this.add(4.99 * quantity); break;
        case "chocolate": this.add(0.45 * quantity); break;
        }
        return true;
    },
    voidLastTransaction : function(){
        this.total -= this.lastTransactionAmount;
        this.lastTransactionAmount = 0;
    },
    // Create a new method applyStaffDiscount here
    applyStaffDiscount: function(employee) {
       switch (employee) {
           case "sally":
               this.name = sally.name;
               this.total = this.total - (this.total * (sally.discountPercent / 100));
               break;
            case "bob":
                this.name = bob.name;
                this.total = this.total - (this.total * (bob.discountPercent / 100));
                break;
            case "me":
                this.name = me.name;
                this.total = this.total - (this.total * (me.discountPercent / 100));
                break;
       }
       return true;
    }
};

cashRegister.scan('eggs',1);
cashRegister.scan('milk',1);
cashRegister.scan('magazine',3);
// Apply your staff discount by passing the 'me' object
// to applyStaffDiscount
cashRegister.applyStaffDiscount("me");

// Show the total bill
console.log('Your bill is '+cashRegister.total.toFixed(2));