Dave Yost, the state's attorney general, said Ohio lets stores have error rates on overcharges as high as 2% but that testing last month at 20 Dollar General stores found error rates ranging from 16.7% to 88.2%.

"This seems like a company trying to make an extra buck and hoping no one will notice," Yost said in a statement. "We've not only noticed but are taking action to stop it."

Dollar General did not immediately respond to a request for comment.

(Reporting by Jonathan Stempel in New York; Editing by Mark Porter)