Your resources will automatically be priced in the buyer’s currency. For example, if you upload a resource to a UK store and price it in GBP, it’ll automatically be converted to USD for US buyers and vice-versa. At present, buyers can purchase in British Pounds, US Dollars, Australian Dollars, Euro (for Ireland), Canadian Dollars, and New Zealand Dollars according to their location.
Your royalty payment will always be in the currency you've set the price of your resource in.
Further information can be found here: https://community.tes.com/threads/uploading-resources-understanding-the-tes-global-catalogue.756027/