Popped into Woolies today.

Girl at the entrance clutching a tablet. Confirmed she was able to check in customers, asked about checking out. She advised that you can do that with the NSW app but she has no way of checking you out (of the store). I persisted but she checked the app and said no options exist.

This makes sense as it would need to either recall your registration or require re-entry to data match. No need for such niceties so you'll have to trust a contact to not register after you've left.

So, if you don't "have" your phone or it doesn't scan you'll just have to keep a manual record of your exit time, then argue the toss if you get pinged. I asked in a smaller store and I might well have asked what the volume of a black hole is.