The days of grocery store cashiers ringing up each item by hand are over. Now they just have to scan a barcode and the product price automatically enters the system. You can even do a self-checkout in many supermarkets.
The scanner not only adds speed to the checkout process, but also accuracy. However, don't assume that the computer is always right. Pricing errors occur more often than you might think -- and it could work out in your favor.
Your cashier might charge you for green peppers when you bought red. Or perhaps something that was supposed to be on sale rang up at regular price. The really interesting thing here is store policy on scanner errors.
For example, in Michigan, if a consumer is overcharged, he or she is entitled to a discount on that item worth 10 times the discrepancy. Sometimes they'll just give you the item for free. So read those receipts, people!