Guys, personally i would advise against sarging at work. Whether it be with co workers or customers, you are just asking for trouble. unwanted advances on your part can lead to complaints and loss of your job.
If you are goign to sarge remember that woman are attracted to power. No offense so please dont take this the wrong way, but cashier.....does not necessary exude power in the work place, it would be much easier to sarge as a manager
...maybe take this as motivation to get that promotion! The best bet is to do your best to appear power full, if there is like an HB 10 if you can offer her anything that the normal customers would not get, give it to her......cupons, discount, extra anything.
Girls love free shit, and if you say "im not supposed to do this but............" you give off the bad boy image as well
good luck