House Tips / Retain Credit Card Tips

We need a way to retain a percentage of credit card tips for the house, to cover the cost of processing those tips.

Right now the closest you can get is with Service Charge on tips. This is no good for 2 reasons:
1. It makes you select what type of card you are running at time of payment, an additional step that will annoy most customers.
2. It doesn't work with Surcharge or Dual Pricing, so it's useless.

Ideally you could just put a % of credit card tips that is retained by the house without having to turn off any other settings or service charges.