[PINeely]

It would be less risky for them to have it say it pumped a certain amount when it actually pumped less. Have the pump display read gallons pumped x a factor of 1.05 for example and same for the price. That way the math would still work out. They know that people are going to be doing the math but nobody is going to drain their tank and measure its contents twice just to see if they're getting screwed out of a few dimes.