In Los Angeles County stores that overcharge customers will have a sign put up that informs the public that the store was caught overcharging customers (via an inspection process) and when they did it. I think this is a good idea, make the stores accountable for the prices their scanners read, especially since the sign is not put up until they are caught multiple times.
Think about Lewis Black when you read this quote:
You’re ripping people off, idiot!
Mr. Blue Sky, that is exactly what I thought. The owner of the store is blaming his workers. They put the sign up on stores that have scanners, so that means the cash register is doing the calculations for the clerk.
Signs like this work. I know I cringe everytime I am about to enter a restaurant that has a B rating (or worse) and will usually go to another food establishment.