UNDATED - This has probably happened to you more than you realize. Items you buy at the grocery store ring up at a higher price than they should.
"It's unfortunately very common for consumers that you go to check out and you realize after the fact that you've been overcharged for something," says SmartMoney.com's Kelly Grant.
Grant says often people never realize they've been overcharged.
With more than 10,000 items in any one grocery store, sometimes shelf and scanner prices don't match. Grant says you need to keep an eye on the prices as you check out.
"Often times it's just a mistake. They have a lot of different items, a lot of different sales. It doesn't always match in the system what's on the store shelf."
Grant recommends you shop with your sales flyer, that you watch that items are not scanned twice and that you check that your coupons are accepted.
What commonly happens, Grant says, is that people don't catch the mistake until they get home.
"They realize it and say, 'It's 5 cents. It's 20 cents but it's not worth me going back to the store to get that money back,'" she says.
Teri Gault, founder of The Grocery Game, says it is possible to recoup the difference, even days after the fact, if you keep your receipt.
In 1998 the Federal Trade Commission estimated the average overcharge at 66 cents.
SmartMoney offers more tips to manage your grocery bill.
Follow WTOP on Twitter.
(Copyright 2011 by WTOP. All Rights Reserved.)