Payment Processing can get very expensive- especially with confusing rates from many of the processors along with their confusing terms. We use a combination of square, stripe, and Wave Accounting for our payments. We use Square and stripe for credit card payments, and Wave accounting for our automated invoices that can be paid via credit card or bank.
there are many other processors out there and while some of them have slightly lower rates, we have found the ease of processing and one flat percentage is worth the few pennies per transaction to keep it simple with the above processors. If you are processing extremely high volumes of Credit card transaction then it does make sense to take a look at others not mentioned above.