There is a method.  First, we said Davis did all of her shopping for "Operation Price Check" at Kroger, but Randalls also has the same policy that if any item scans incorrectly at the register, the customer gets one of that item for free. The cashiers won't always tell the customer about the refund. Here's how to make sure you get one.

We all know no one likes the customer who holds up the line haggling over 20 cents. Davis has gotten some pretty dirty looks herself. Instead of watching the prices like a hawk at the checkout, take some paper and a pen with you when you shop and write down the price of every item you put in your basket.

After you pay, take your receipt and wheel your cart out of the way, but not out of the store.

You want to make sure the prices on your receipt match the prices you marked on your list. If you find any errors, circle them. Then take the receipt and your purchases to the customer service booth and tell them you want a refund on those items because they scanned incorrectly.

"It sounds like a good policy," said Lee. "They've always been good about changing it at the register. I just wasn't aware you could actually get a free item."

"There are between 70,000 and 120,000 items in every store and with thousands of price changes each week, unintentional errors may occur," said King. "And when you find those, please bring those to our attention and you'll be compensated for them."

Kroger's policy only applies to items without a price tag on the package. The store will not give you a refund for alcohol or tobacco.  Randalls' policy applies to everything except alcohol, tobacco and dairy products. We checked with both H-E-B and Walmart, but neither of those stores has a price guarantee policy.