Behind the scenes POLi is literally logging into your banking on a virtual machine hosted in AWS. Because of this, it is also very easy for banks to detect POLi and mark it in their fraud detection systems. From this point you're actually breaking the internet banking terms of conditions with most banks since you handed over your details to a third party.
Just don't do it, ever.
First off payments can't be reversed or dishonored if made (you get no buyer protection) and second even if they don't have a record of fraud it doesn't take much for somebody to scrape your details. Using a Credit Card / Debit Card instead gives you buyer protection and fraud protection shopping online.
We suggest you stay safe doing your festive shopping and use an alternative form of payment.