I would imagine that unless you're buying massive quantities of components ,no one's going to come after anyone for something like this.
The transaction between whoever makes a purchase and the seller is legal , because the buyer pays tax(& newegg charges tax) ,so I don't see how this is going to affect anybody in anyway shape or form.
The IRS comes for revenue ,that's why it's in their name ... it's up to the seller to charge the buyer tax depending on their state ,and for the seller to report that tax to the government. If for example someone bought the components for a computer ,and build it ,and provided it to a third-party at no additional cost (over sale price) there would be nothing to report ,because they never charged anything ,and therefore unless the person they gave it to lied to the irs, theres no problem, and if a problem does arise, it would be for the 3rd party.