[jusssi]

Is it the sort of deal where the cash goes straight to the pocket and you don't get a receipt?

And no, you don't need to go south to find those deals.

[Symbiote]

In Denmark, it's not so unusual for there to be one price for cash or debit card, and a surcharge for credit cards, especially foreign ones.

They aren't fiddling the tax. Credit and foreign cards cost extra to process.