$10 is a bit of a stretch. Local guys I go to have a $5 one but it's mainly for blow in off the street who want a bottle of water and want to pay on card. Generally if you bought heaps of stuff, walked out and on the way out forgot something and it costs around $3 they let you pay wave it.
I've seen restaurants with $15 and $20 minimums. It's ridiculous.
They would get charged more because they are in a lower revenue bracket so the bank would slug them a fair bit.
I saw one pizza place do a 5% discount if you pay cash, probably is the better way to go.