In the UK quite often smaller shops will give discounts for cash purchases or add a surcharge if a card. I always ask if they give discount for cash, sometimes it works sometimes it doesnt.
Tescos used to have on there recepit something about 2.75ish percent of charge for customers paying with card, but 0 percent for cash purchasers. But you pay the same amount at the till. I think they must have been having a dig at the card companies.
Ikea now charge 70 p for card transactions.
So u cant charge more but im sure they will be able to offer a discount for cash or some work round. That or like a lot of shops in phill not accept them.