My question is very similar to this one on SO, only it doesn't exactly help me because it talks about replacing the currency symbol in front of the price and not displaying something after it.
What I would like to do is display after totals on the checkout, cart and other pages like that the price in this format: $232.00 AUD - the price will always have AUD on the end as it is an Australian run store.
Is there an easy way of doing this without having to edit multiple templates and resort to hacky conditional if statements?
If your prices always ends with ".00" you can use CurrencyManager module from related topic answer. In this case you can set option "Cut Zero Decimals" to "Yes", and option "Replaces Cuted Zero Decimals" to ".00 AUD".
If you have cents in your prices you need to change
public function formatTxt($price, $options=array()
in /app/code/community/ET/CurrencyManager/Model/Currency.php if you will use this module, or rewrite this original function in core (/app/code/core/Mage/Directory/Model/Currency.php) by own module.