Required accuracy / resolution of truck scales?

I actually just weighed my car the other day at a scrap metal place that has a drive on scale.

I did wonder how accurate their scale was but you gotta think that it would behoove them to keep it as accurate as possible since they are paying out for weight. Can't image they would want to pay a penny more, right? It could also work the other way where if guys knew they had a stingy scale they would take their business elsewhere.

I'm sticking by that logic. :D