The curmudgeonly answer: I would consider if the person is providing some service above and beyond what someone in their position would normally do, and if not, the answer is usually no. I think the tipping thing in the U.S. has been getting out of control, especially post-Covid. I see tip jars all over: in grocery stores, gift shops, auto shops, etc.
The nice-guy answer: if you go there a lot, you like the people and you want to show some gratitude (which is basically the definition of "gratuity"), and you know that the employee pockets ALL of the tip, then by all means drop a buck or two. Follow your heart. Just do it. I'd probably do so if I were in your shoes.