OT, but on my first week in Oz I had bought a cup of coffee for $4 (I could see them, they're four small copper coins.) then went through my pockets to get rid

OT, but on my first week in Oz I had bought a cup of coffee for $4 (I could see them, they're four small copper coins.) then went through my pockets to get rid of small change as tips, much to the waitress' resistance. So I gave her something around 6 - 10 smaller copper coins, much smaller than $1 coin. Turns out, the smaller coins are actually worth $2, and I must have given her $12-$20 worth of tips for a cup of coffee.