A lot of people forget there is a cost for a business to use cash too.
I don't know what it would add up to or how it compares to the CC fee but there is an definite cost.

Labour for one, anger at the till making change than tapping and go then the labour time to add up the cash, sort it, compare to register amount and reconcile then prepare a deposit and transport it to the bank 
Banks charge a fee for the account based on what or how you are using it.
If your account has not paid for the privilege to deposit a larger amount then there is a % charged for them to accept cash.
Then there is the cost of running to the bank to get another couple rolls of Loonies or Toonies or quarters etc to be able to make change.  Do the banks charge to give you a roll of coins for paper money? There is a labour cost for someone to make the trip and yes I know it happens as recently when cashing out they were getting some twenties out of cash drawer to take to bank to get more change.
they were glad when I reached in my coat pocket and pulled out a handful of loonies and toonies, quarters and dimes so was able to pay the les than $10 in coin