Here it's the customs office through the mail service (which carries the delivery service once the parcel is in the country) who handles the taxes expenses. They usually confirm they have a parcel for you and ask for a payment receipt or an invoice, then they add the shipping cost and calculate the taxes and fees. Once you agree and wire payment, they delivery the goods. There are few cases, when the parcel is not very expensive or large, that they calculate the taxes so you pay them to the deliverer.
I guess that each country would have its own procedures, it's possible that at some places it's EMS who acts as agent handling the import papers directly, then charging them to you, as Fedex or UPS would do. You're very likely to get better information if you contact your local EMS representatives.