Visa and MasterCard will sue you (and disconnect you Point of Sale device really quickly) if you try and pass those costs transparently onto the customer - they

Visa and MasterCard will sue you (and disconnect you Point of Sale device really quickly) if you try and pass those costs transparently onto the customer - they've loosened the rules a bit for minimum purchase quantities (i.e. 5$ minimum for credit card purchase) but if you try charging an extra x% of the listed price when people pay with credit card they will go after you hard.