Many cash registers can Integrate Credit Card Payments with the use of a Datacap Product like the Twin Tran or the 162SL. We like to use the SAM4s or Sharp Cash Register when Interfacing to Credit Card. Most of the SAM4s and Sharp Cash Register Line Up can have Integrated Credit Card Payments.
One company offers the hardware at little to no cost when you process through them. And they offer a Free Gift Card program as well.