Declare Tax, Shipping, and Handling Costs with Active Merchant + PayPal
I didn't see this documented anywhere but with Active Merchant + PayPal Website Payments Pro or Express, a breakdown of the order total can be specified.
gateway = ActiveMerchant::Billing::PaypalCaGateway.new(options)
gateway.purchase(8475, credit_card, {
:subtotal => 7500,
:shipping => 0,
:handling => 0,
:tax => 975
})
Subtotal, shipping, handling, and tax values must all be there and they must all add up to the order total ($84.75 in this example). View the relevant code at Github