How to taper off sertraline?

You must do it very gradually under medical supervision provided with a discontinuation schedule by your Dr. and under constant guidance by him/her in order to minimize/avoid withdrawals.
Your Dr. is responsible for your treatment and safety.

"Do not stop using sertraline suddenly, or you could have unpleasant symptoms (such as agitation, confusion, tingling or electric shock feelings). Ask your doctor before stopping the medicine."

Source: https://www.drugs.com/sertraline.html