In a business context, I've never understood the ethics of tipping. It has a bias for youth and feminine gender and thus I must not use qualitative inputs when determining my tips without fear of a subconscious bias to cause me to improperly spend my companies money in a way that may be unethical or possibly illegal (as both age and gender discrimination are real and I'd like to avoid them). For this reason, I tip 10% on business trips always when it is requested and regardless of service quality.

Anything else just seems too close to the definition of graft or bribery for me to feel comfortable.