I had a type of DCC notification that I'd not seen before at an Ibis hotel in Thailand. The system outputs a separate printout offering THB or your home currency. It lists the exchange rate being used and claims a mark-up of 3.00%. Then you choose whether to be ripped off or not and your final receipt is printed separately.

In reality, the amount quoted for USD would have been 4.77% more than the amount the THB charge converted to.