I'm from NSW, and David Jones and Myer have already completed their CC applicant/group interview stage a loooong time ago. Unless their doing a second round, I think they've already finished the recruitment stage.
Not sure about other states.
You could try JB Hi Fi or Event Cinemas. Just ask and hand in a resume. Cinemas will need people during the summer holiday buzz. A lot of retail clothing stores have already finishing their recruitment stage. Maybe just browse the websites and see if they have anything open.
Apply now!! Do not wait till after the HSC. I did last year, and could not find anything, ANYWHERE. (My best friend did get a CC position last year in Payless Shoes straight after the HSC, so maybe their worth a try.) But this year I applied early in August-September, and got lots of offers. So it definitely pays to apply early, because my resume really hasn't changed much since last year.
Good luck!