I had a close friend who worked with Border Force. He assured me you can and gave me a copy of the declaration form in case I needed to take $10,000 or more. If you don't have one filled in, when they ask if you are carrying $10,000 or more and you answer yes, they will take you aside and have you complete the form. Before you give misinformation, go to the web site and check.
There is no limit on cash you can carry leaving Australia. If you have AUD10,000 or more (or equivalent in another currency) just declare it and you are good to go,