I know they have scales in the produce section, but I don't think I've ever actually used one. It's something I'll do occasionally if I'm buying from a bulk bin, but fruit or vegetables I just grab however many I think I"m going to need.
I buy my produce "just in time", so I'm frequently using those scales to be sure that I've purchased as close to exactly what I need as possible for what I'm making that day. I don't want leftover produce.
For example, I made two apple pies the other day. The recipe calls for 2 lbs of apples each, so I bought 5 lbs of apples (to account for the weight loss from coring and peeling).
Or, just over charge by a large enough margin to make up for it.