Urgent Tax Question

I'm going to order lots of phone cases from a Chinese company. They are going to ship it by DHL. Please tell me anything you know about tax that I'll have to pay? How much will that be and what papers will I have to fill out? If you can share a link to a government website or a source where this question is thoroughly discussed, that will be very much appreciated! Thanks.

The most important detail that you did not mention is the country of residence, it's impossible to help you without it.

I forgot to mention the main part, I'm in the USA.

Another great question is how much $ it's worth...and how much the chinese will declare to customs