One does not need to tip in Australia under any circumstances. 

Whilst certain tour companies, high end hotels, and dining establishments are trying to pass the wage burden on to less than suspecting foreigners, via requests in tour literature, influencing guide books, web articles, certain newspapers, etc one shouldn't feel obligated to tip in any situation whatsoever in Australia. Australians, by and large, don't tip.

It is not legal for a restaurant to add anything to any bill that is not specified in the menu. Always ask for change if there is any hesitation from anyone that serves you; because you happen to be a vistor from a foreign country where tipping is customary. 

The reason why tipping is not required, under any circumstances in Australia, is because every worker in Australia is legally entitled to a decent/livable wage (without any tipping), 4 weeks paid leave, paid sick leave and superannuation (retirement savings) OR a very high hourly rate and thus tipping is absolutely not necessary to supplement a worker's life style.  

That being said, taxi drivers, wait staff at high end establisments, or porters will not say no to a tip. But anything more than 5% to 10% would be considered extraordinary