I ship internationally all the time. I only have to declare what the items are and what their approximate value is. The duties or tariffs are the responsibility of the receiving party. If your postal worker does not collect from you at the time of delivery a few things could still happen:

1. You will receive a bill from the shipper who paid the tariff at entry - this happens to me on international shipments I get on raw materials/component parts.
2. You were not assessed a tariff
3. What you imported was not subject to tariff