Upvote:3
Just carry Australian dollars because every transition between currencies loses you money on unfavourable rates and/or commission.
The only benefit to transitioning through US dollars is if you feel that the currency fluctuations will make it worthwhile enough to more than cover the exchanger's margin, which is nearly impossible to pick for anyone that isn't a currency dealer.
Upvote:5
Buy Australian dollars, and you're probably better off exchanging them in Bangladesh. The taka is a weak currency and you would likely get a bad rate for it in Australia.
Also, if you want to exchange larger amounts, I would recommend alternative routes like ATM withdrawal or money transfer instead of cash.