I shun JWs. There is nothing they have that I want or need, and there is nothing to like about them. I stopped doing business with them many years before I left the cult because too many of them have a poor work ethic. Many act as though secular work is nothing more than a necessary evil. I remember being counselled once because I said in a conversation that I found my work interesting, and liked going to work.
I wouldn't necessarily stop doing business with a company I liked, but I would make it clear to management that I didn't want to be served by a JW that was shunning me, or giving me poor service because of my religious choices. I would report the Petsmart employee to the store manager. Obviously she lacks the professionalism to separate her religious beliefs from customer service. Her choice of religion should not be your problem, or Petsmart's. She needs to have her ass fired out the door.
Be prepared to have your family call looking for favours. The shunning often stops when they need money. Or they might tell you about an upcoming wedding in the family, so you'll feel obligated to send a gift, even though you won't be allowed to attend. Take the opportunity to remind them you have been disowned, and that disowning should work both ways, and not only for their convenience.