John wrote: Every
I don't know whether or not it is still true but at one time merchant's contracts with the c.c. companies prohibited their doing that. Some try and succeed with customers who aren't (weren't) aware of it. Twice I was in a situation where my purchase was a dollar or so below the "minimum' and the cashier asked for a different method of payment. When I challenged the policy, my card was accepted with no further questions.
Rita