Currency Conversion at Checkout

-- HikaShop version -- : 2.3.5
-- Joomla version -- : 3.3.6

Hi - I decided to try adding the currency conversion to the store. Works perfectly, however when the payment goes through PayPal, it is paid in the currency that the customer has chosen. Then you need to convert the currency back to your location - eg. US to AUD which adds more costs/fees in conversion rates.
Can I display the currency convertor for the customers convenience but it only accept payment in AUD when checking out?

Thanks.

Thank you Nicolas - that works except when going to the checkout it has the following message (although if I ignore it, it appears to be ready to accept the payment via PayPal):
Message
The currency you selected is not accepted for payments

Yep - that did the trick.
Many Thanks