Bali uses the Indonesian Rupiah.
ATMs can be found all throughout Bali, particularly in the main tourist areas and shopping districts. If you plan on withdrawing money or using your credit card while travelling, don't forget to notify your bank before you go for security purposes.
Before you leave home don't forget to convert some of your Australian Dollars into rupiah to have with you when you arrive in Bali.
Traveller's cheques can be purchased from Travel Money Oz, allowing for safe spending while overseas. Similar to cash, traveller's cheques can be used at most banks when you need cash. Some transaction fees may apply.