No currency conversion rate in REST API when using Shopify Payments?

Hi all,

A client of ours recently started using Shopify Payments, and had a customer purchase from the EUR shop using USD. Over the API we can see the total of the order in EUR and the payment in USD, but no currency conversion rates. Is there a way to find the EUR value of the payment, or should we just assume that what ever was still due on that order before the foreign currency payment is always paid completely and calculate the currency conversion rate from there?

We’re moving the orders to a bookkeeping system so we’d prefer not to assume anything if we can get the data somehow.