OK, I was buying make up. I went to one store where they insisted on helping even though I didn't want it and then helped in a fake friendly kinda look-at-the-guy-who-wants-to-be-a-girl-so-lets-laugh-at-him way. I left there and eventually ended up at Macy's, ½ hour or so before they closed. There, I had three makeup artists helping me very earnestly as there was no one else there. At first, I was embarrassed but they were so nice that I got over it. I really needed the help and help they did. Not recommending that as Macy's is expensive but they were so helpful.
In the end, it all depends. I think the tellers smell fear the way some people think dogs smell fear. Walk up, be confident, know what you are doing and it works. Don't walk up in ignorance and expect no response. Don't look guilty. Don't make up a story (that really backfired for me.) If they ask, ignore them or answer them, your choice.