FYI, there have been a few posts on this, so you can catch up on previous responses here.

• Why did Australia and NZ (and Canada?) switch from Pounds to the Dollar back in the 50's / 60's?

• Why do Commonwealth countries like Canada, New Zealand, and Australia call their currencies "Dollars" as opposed to "Pounds" in keeping of British tradition?

• How did the word dollar originate?

Colonial possessions that developed into dominions and later independent countries such as Australia, New Zealand, and Canada, each established their own Reserve Banks throughout the early 20th century and issued their own currency as a means of gaining greater economic autonomy and growth.