Not sure when it ends but it's part of their Double Cash Back Weekend for Black Friday.
Not sure if there's a cap or per transaction/user. Can't find any T&Cs and there wasn't an email notification.
I just spent ~$60AUD on Friday too -_-
Check if you have a bonus $2.50 on $15 spend too. This one expires 11/26/2023 11:59:00 PT which should be Sunday 27th 6:59 PM AEDT.
Coming up as 10.5% cashback for Australia, 15% cashback is for USA I believe (Correct me if I'm wrong)