Has anyone tried to purchase from an international site? How are the goods shipped? Does it pass through customs and claimed through the post office?

Normally when I purchase items from US online retailers (Amazon, Nordstrom or Saks etc), I have it shipped to a relative's US address, when my items are enough to fill a box, they send it through sea freight (LBC) which takes about a month to arrive in the Philippines. This is delivered directly to my home.

Recently I was offered free international shipping by a US online retailer which I want to take advantage of. Will the items pass through the post office or customs? I've heard so many horror stories on claiming items from the post office and customs taxing above the value of the items.