In Reply to: attention math people posted by mellee on Thursday, 22. April 2010 at 20:29 Bali Time:
From my own experience, I've always received within a dollar or two of what I was expecting (as checked the night before on the oanda website).
So, going off that and based on the rates I just looked up, you're looking at AUD$28 for your US$25 visa. AUD$22 change converted to rupiah should be Rp177K, so you'd probably get Rp160-170K-ish in change.
But as Holladaze said, it will depend on the exchange rate n the day you go, and the person at the counter when you get there.