Wow, some people on here can be real dicks.
I agree with not asking a woman out while she's shopping at your store. However, there's nothing wrong with some casual flirting.
If you're a good salesperson, entering into conversation shouldn't be all that hard stemming from a discussion about the products. If she's interested, she'll talk.
1. Don't be too blatant about it or your boss might get pissed off
2. If she's got a wedding band...