Bad idea because companies will frame it as “going the cashier route will cost you 10% more!” while you pay the old price st the self check-out. Here in Europe a lot of groceries are being shoplifted at the self checkout. People are taking their own discounts. Newer self checkouts now have cameras built in and random controls are so freqent they are a huge annoyance. Spermarkets seem to be pissed.