Sales Quotes defult to $US when the base currency is set at $AU

I am new to Manager and can not work out why my sales quotes are now defaulting to $US when the base currency is set at $AU. The items are stored in my inventory as $AU but the quotes continue to default to $US even when I delete the item/s and re-enter the inventory details. Can anyone assist?

Sales quote currency is determined by the currency of customer. When you go to Customers tab and edit the customer for which the quote is being issued, what is selected under Currency field of the customer?