should be the standard retail wage which varies state to state, look up award rates for your state and then your age, and if you are a manager you will need to look up the difference on that aswell. Should all be on the local government site.
us queenslanders get a lower rate per hour then those nsw bastards. haha. and different companies have different enterprise bargaining agreements. there are a heap of different variables to take into account.
I know at coles in queensland for a casual rates go abit like this
16 = $10 ish p/h
17 = $11 ish p/h
18 = $14 ish p/h
19 = $18 ish p/h
20 = $20 ish p/h
21 = $21 ish p/h
Im sure it wouldnt be much higher then any of those rates.
.. Mind you, older you are, if your above 18 they don't raelly like to give you many shifts, only as many as they have to (there needs to be a few due to things that need to be done. example : cigs and crap).