Here's why every business in the DR doesn't want you to pay with a credit card. It's not really the fees they pay to Visa, MasterCard, etc. It's that they're cheating the government out of the sales tax by grossly under representing the true volume of their transactions. When you pay by credit, it makes it easier for the government auditors to catch them. We were there when the DR version of the IRS (I'm American) did some sting operations on the beach front restaurants.
While it's nice not to pay the tax and have money for another pina colada, I would rather pay it and have a sounder infrastructure on the island.
Favorite thing: There was a Cuban man called Rafael who made the nicest drawings of you in cartoonstyle. Because we are both firefighters this is what he made of us.