PC Build, do I still need to pay taxes? How do mail in rebates work?

[Low Profile Gamer]

Hello everyone, I will go to California next week, and my cousin and I are going to build a PC. Here are the parts I chose:

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Pentium G4400 3.3GHz Dual-Core Processor ($57.99 @ SuperBiiz)
Motherboard: Gigabyte GA-H110M-A Micro ATX LGA1151 Motherboard ($45.99 @ Newegg)
Memory: G.Skill NT Series 8GB (1 x 8GB) DDR4-2400 Memory ($32.98 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($47.49 @ OutletPC)
Video Card: Zotac GeForce GTX 750 Ti 2GB Video Card ($94.89 @ SuperBiiz)
Case: Rosewill FBM-02 MicroATX Mini Tower Case ($21.99 @ Newegg)
Power Supply: EVGA 430W 80+ Certified ATX Power Supply ($18.98 @ Newegg)
Total: $320.31
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-08-19 17:04 EDT-0400

My questions are:

Do I still need to pay for taxes, or is it already included in the price, just as PCPartPicker says?

I saw a $15 mail-in rebate for the power supply, how do I use that? Do I have to be a resident in order to use that? I will be paying using a mastercard from another country, will that be eligible for a mail-in rebate?

 

[rgd1101]

"when available", don't mean included

rebate usually for us address, check the rebate form for detail

 

[Low Profile Gamer]

"when available", don't mean included

rebate usually for us address, check the rebate form for detail

Thanks for pointing that out, it seems that I'd have to pay 8.25% tax, which I hope they would already debit in my card as I purchase the products. I won't be counting on the mail-in rebate anymore, though I still want the EVGA PSU.

 

[rgd1101]

Yes, the tax should included when you purchase them online. if not, I wouldn't worry about it.