I worked in retail before. We sold leather (mostly motorcycle leather) but some was a tad more form fitting. Some clerks are cool with TS, some aren't. I was the open minded one of the place, so I was always glad to help whoever with whatever. I was never paid commission. I got paid regardless of if anyone bought anything. But it always made me feel better when someone walked away feeling happy about themselves, and hopefully with something I helped them pick out. (plus it was a LOT of fun sizing people for chaps!!!)
As far as bras go, more than front or back closure I think it's about the actual cut and shape of the bra. It does seem to me that front closure bras tend to do a slightly better job of enhancing what is already there. Plus front closure bras are FUN to undo.