You have:
<ItemTotal currencyID="AUD">9.09</ItemTotal>
but in your cart you have:
<PaymentDetailsItem><Name>Test Item</Name><Amount currencyID="AUD">10</Amount><Quantity>1</Quantity><Number>1474</Number></PaymentDetailsItem>
So your item total doesn't add up to the amount of the items in the cart. You are probably doing a discount on the items and need to pass the discounted amount in the item details.