While researching stays in Copenhagen on Booking.com I noted several hotels stated read the fine print for potential extra fees. The fee is 1.25%-3.75% for using a foreign (not just USA) credit card and/or debit car for purchases in many businesses. Businesses are not necessarily required to post the Gebry=Fee but many do. A google search showed the topic on FlyerTalk back to 2009.
This is not DCC. One example, the bill is 600 local currency and the screen in local currency is 618. It is a fee.
For my travels, I will consider hotel/restaurant that do not charge the fee. Consider cash versus cost versus CC easy use.