Cash discount credit card processing was developed to allow merchants to offset the cost of credit card processing costs by charging a service fee on all transactions and giving a cash discount to those who pay cash.
The vast majority of merchants find the saving to more than offset any negative. Saving a couple percent in processing fees, could net you a double digit increase in your profit margin as your overhead costs should remain steady. The savings of a couple of percentage points on every sale can quickly offset a small amount of potential lost revenue.
The process to convert is pretty simple once you have your new agreement and hardware, you will post signage are your store entrance and the point of sale disclosing the fees. Current statute in Minnesota also requires you to verbally disclose this to your customers.
You need to treat all of your customers the same so you can not selectively charge a service fee to one customer and not another. If you have a service or price point that does not make business sense to offer cash discount you may have second account to process another way, remember you still need to treat all customers the same, and treat all card brands the same you can not charge a different manner based on the card brand the customer is using.