The following is my response on a blog which posted the above question. They have been deleting responses, so though my response would be safe here:)
I was just going to comment on the how to deal with the tip line until I read all the replies and noticed that many people referred to the point of sale (POS) system functions. I am with Sintel Systems and we provide POS systems to a variety of industries, so I will address and try to clarify both issues.
1. Tip Line: Tipping is a function of the service you receive. As an example, when I get my coffee to go in the morning, I typically tip because I enjoy the extra effort the person puts in greeting me and smiling. That to me is good customer service. There is a tip jar there so when I pay with a credit card, I write “Cash” on the tip line, write the total, and put the cash in the jar. Tipping in any case is optional and is meant to correspond to the level of service you receive.
2. Point of Sale – There are two components to the POS system which allow for the generation of the tip line. Our systems integrate the POS system with the credit card/merchant account, but they are technically still two components.
First, there is manner in which the credit card/merchant account is set up. Typically with food-related places there are two ways the can be set up. Either 1) Restaurant or 2) Retail. As an example, our frozen yogurt clients are set up as retail while all our pizza customers are set up as restaurant. The establishment can only accept tips if its merchant account is set up as restaurant.
Second is the POS system set up. As an example, the administrator can set up the software to accept tips or not. So it is up to the owner to include this line or not. However, an owner can choose to add the tip line with the POS software on a systems which is set up as a retail operation, but even if you put the tip on there, the merchant account will not process it. This is probably what happened in regards to the comment posted regarding the US National Park incident. It was the POS system that was programmed and not the credit card machine.
Bottom Line: Tip for the right service.