Adding sales tax to invoice?

hi, i recently quoted a client for a project and now im wondering if i can/should add sales tax to their bill totals?

if im charging the client $x/hr for 10 hours, can i put 10x in the invoice for the projec sub-total and s% for the sales tax?

reason i ask two:

  1. can a development company do this or do they have to include sales tax in their hourly rate?
  2. the government will be taking taxes from me, so if i dont include sales tax, im actually not making 10x, but rather 10x - tax.

Any thoughts?
Thank you!