You must convert money figures so Australians understand values. It's no use telling your readers that something costs eight pounds or 2000 yen or 40 roubles or 100 euros, unless you convert it to Australian dollars. And use the WORDS for foreign currency not the signs, like for English pounds or for Japanese yen. So, write like this: In Tokyo a Big Mac costs 70 yen (A$3.50), while in London it costs four pounds (A$2.25). My conversions are not accurate but your conversions must be. Double check, please. For a free, up-to-the-minute, easy-to-use currency converter, log on to www.xe.com and use your calculator.
The principle here is bigger than money. Your reader thinks in the units they live with: dollars, kilometres, kilograms, degrees Celsius. The moment you hand them a figure in someone else's units, you make them stop and do sums, and a reader doing sums is a reader who has left your story. So you do the converting for them, every time, as a courtesy and a duty.
It applies right across your copy, not just to currency. A distance in miles becomes kilometres. A weight in pounds becomes kilograms. A temperature in Fahrenheit becomes Celsius. An American "billion" and an old British "billion" once meant different numbers, so when in doubt, spell out the actual figure. Always give your reader the version that lands in their head without effort.
Two cautions when you convert. First, accuracy, exactly as I warned: exchange rates move every day, so check the rate on the day you file, and note it if the figure is important, because a conversion that was right last month may be wrong today. Second, do not pretend to a false precision. If a thing costs "about four pounds", then "about ten dollars" is honest, while "ten dollars and seventeen cents" is a nonsense that suggests an accuracy you do not have. Convert faithfully, round sensibly, and your reader sails through.