Usage of tips is a common feature of several industries (including restaurant industry, beauty saloons etc.). Originally, tips were given in cash. However, if credit card processing is involved, tip should be added to the amount of the main purchase. The traditional way of handling tips when a customer pays with a card was called tip adjustment. The tip was specified on the receipt, added to the main transaction, and processed together with the main amount.
With the advance of EMV liability shift many companies started searching for new card-present solutions. The innovations concerned both payment terminals and POS software. Particularly, if a customer needs to input PIN to pay, he has to contact with the payment terminal. But if he does that, he can also input the tip amount himself (providing, the respective functionality is supported by payment terminal software). This will allow the merchant (restaurant industry player) to perform tip adjustment before transaction is authorized.
There is another important feature, which merchants and POS software developers should consider. We are talking about support of a tip, addressed to multiple recipients. Beside restaurants, this function is particularly relevant for beauty salons.
More information about tip adjustment, restaurant POS software, and restaurant credit card processing, can be found in the respective article on Paylosophy.