How much do you tip for a $50 pedicure?

I'm curious, when it comes to tipping for a $50 pedicure, what's the standard amount that people tend to give? Is it customary to tip a flat rate, or is it more common to tip a percentage of the total cost? And if it's a percentage, what's the typical range that people follow? I'd like to make sure I'm being respectful and generous, but also not overdoing it. So, how much do you typically tip for a $50 pedicure?