allow for preferred currency

app/controllers/checkout_controller_decorator.rb

@@ -217,7 +217,7 @@ CheckoutController.class_eval do
 
   # hook to override paypal site options
   def paypal_site_opts
-    {}
+    {:currency => payment_method.preferred_currency}
   end
 
   def order_opts(order, payment_method, stage)

app/models/billing_integration/paypal_express.rb

@@ -4,6 +4,7 @@ class BillingIntegration::PaypalExpress < BillingIntegration
   preference :signature, :string
   preference :review, :boolean, :default => false
   preference :no_shipping, :boolean, :default => false
+  preference :currency, :string, :default => 'USD'
 
   def provider_class
     ActiveMerchant::Billing::PaypalExpressGateway

app/models/paypal_account.rb

@@ -8,7 +8,7 @@ class PaypalAccount < ActiveRecord::Base
   def capture(payment)
     authorization = find_authorization(payment)
 
-    ppx_response = payment.payment_method.provider.capture((100 * payment.amount).to_i, authorization.params["transaction_id"])
+    ppx_response = payment.payment_method.provider.capture((100 * payment.amount).to_i, authorization.params["transaction_id"], :currency => payment.payment_method.preferred_currency)
     if ppx_response.success?
       record_log payment, ppx_response
       payment.complete