Eventually, she was banned from two New England supermarket chains. They say she was taking advantage, but she says stores are.
"It may only be 2 percent but when you think of how much money Americans spend on a lot of items that's a lot of money," she said.
The Food Marketing Institute, which represents grocery chains, told "GMA" that supermarkets strive for 100 percent price accuracy even though an average store stocks about 45,000 different products, and that in a recent national study, supermarkets had the best accuracy rate of any industry, but that shoppers should immediately report discrepancies.
You should either jot down shelf prices or snap a cell phone picture of them. If you don't want to do every item, then choose a few – maybe 10 or 12 – and spot check.
If you can't keep up at checkout, review your receipt before you leave the store parking lot so you don't have to schlep back for a few cents' correction.
And for more motivation, find out which stores offer you items free if they ring up wrong.
If you find a pattern of overcharges, as opposed to a few innocent mistakes, complain to your city, county or state weights and measures department.
If you want to complain about overcharging at a grocery store – or any type of store – contact the state department that oversees the issue. Click HERE for a list of those agencies, listed by state.