I pretty much routinely tip 20% for food, alcohol, and taxis. ** but see below.
If I'm at a bar drinking beers, I put a dollar on the bar for each beer I drink.
**For the first time in my life, I gave a taxi driver NO TIP. We drove from Manhattan to JFK. My phone app showed a huge backup along the Grand Central parkway bc of an accident. I said "please take the Van Wyck, not Grand Central." He said no, he preferred Grand Central. I showed him the traffic on my app, and said "take the Van Wyck". He said no. I pointed to the Van Wyck as we got close and said "go there, go there, there, the Van Wyck. No, don't turn right onto Grand Central, don't do it." He turned right onto Grand Central. It took an extra half hour to get to the airport. I made it right to the gate as the plane was boarding.
NO TIP.