Lets say you get up one morning to go to the donut shop to grab something to eat. You find out you don’t have any cash on hand but plastic. Your bill came out to $2.25 and you hand them your card. They then point to a sign that says $5 minimum purchase for credit card transactions. You get upset and may or may not complete your purchase. But you wonder, is this allowed? The answer is no, even though many merchants enforce this policy. It is against Visa/MC rules. There are other things you can do such as a cash discount, but you can not refuse a credit card sale regardless of the amount.
If yourcompany finds out, they will immediately terminate your account and it may be impossible to ever get one again. So I highly recommend against this practice, it just doesn’t work out overall to benefit the merchant. How many customers will you alienate in the process? I totally agree that it can be difficult to manage the cost when dealing with such low transaction sizes, but consider this. That same customer may come back or is a regular that will spend a lot more next time when he has his family with them.