Its not required that your employee leave a tip for the hotel staff. I don't no matter what * level the hotel is. Once again, the staff at these places are being paid a wage to do a job. It is their job to clean your room and make up the bed. Its not your employee's job to try and make up for the wages he feels the hotel should be paying the staff.

So having said that, he shouldn't be leaving a tip on the dime of the company that is paying your company for services. If he insists on paying a tip he needs to pay it from his personal funds.