Customs taxes in Taiwan (Taipei)

Hi,

If I order something online from outside of Taiwan lets say USA how much taxes should I expect to pay to the customs. Is it based on the money I payed (fixed %) or it depends on smth else as well? I'm just trying to calculate if it makes any sense to buy online or if it's going to be too expensive.

Also if whatever I'm buying is subject to customs taxation how do I collect my package ? Do I get a ticket to pick it up from customs or post or..?

Thanks a lot!