Set a service fee for accepting CC on orders for less than $10.   Or, all orders on the cart.  how many order does one get that are $30 or $40?  It could be waved for large orders.    …… Processing fee plus a percentage, say 75 cents or $1.   Then it is the customer’s choice. 

… If most of your sells are $8 to $15, you may be slightly behind on your CC cost, but the difference should reasonable & acceptable.  If your sells are small then you should be a little ahead on CC cost.

Remember not long ago, many business had two prices cash & CC.

Every merchant agreement that I’ve seen states that you cannot charge a service fee or “minimum” purchase. The people that do this are in violation of their merchant agreement. If someone calls to complain, their merchant account will probably be pulled. I know someone that this happened to. They had a $15 minimum charge. In my prior business, I offered a discount for cash instead of a service fee for credit. (probably still could’ve lost the merchant account)
 
But if you lose a merchant account, you can easily find another bank or processing service.