Yes!  Tipping is the commonly accepted practice to show appreciation for a job well done.  Tattooing is a service industry like barbers and hairdressers.
As a guideline, the normal range is 10-20%, although we appreciate whatever you may feel is appropriate.
For multi-session tattoos, it is customary to leave a smaller tip after each session, rather than leaving a large tip at the end.
Keep in mind that tips are accepted in cash only.
Thank you very much!