You are out grocery shopping, and after you have placed all of your purchases in your basket, it is time to go to the checkout line. As the cashier scans your goods, you notice that one of the items...

You are out grocery shopping, and after you have placed all of your purchases in your basket, it is time to go to the checkout line. As the cashier scans your goods, you notice that one of the items does not seem to be displaying the stated discount on the register. What might be causing this to occur?