I was there earlier this year. I found that many businesses, and especially restaurants and public services, would not accept cash. However, when I did pay for something in cash, I immediately came to regret it. Australian coins, known locally as "shrapnel", are very large and very heavy.
I recently passed through Austin TX airport and bought dinner at ‘Salt Lick BBQ’ which served am undersmoked brisket that had an ridiculously overly sugary sauce dumped on it. I was told I could not use cash and had to pay by card.