They have a maximum they will accept in each coin According to the Currency Act 1965 (section 16), Australian coins are legal tender for payment as long as they do not: - exceed $5 of any combination of 5 cent, 10 cent, 20 cent and 50 cent coins are offered. That means for example, you can only use 100 single 5 cent pieces in a transaction. - exceed 10 times the face value of the coin if $1 or $2 coins are offered. That means, you can only use 10 $1 coins, or $2 coins for a transaction.