My wife and I always make sure to have 20s, 10s, 5s and 1s when we go out. I prefer using cash. We tip at least 20%, usually more. Most of the servers in our area will say something like "I'll be right back with your change" and we'll tell them to keep it. During these crazy times we also leave tips even if we are picking up an order. Small businesses and their help have been hit hard by this nonsense.