sales tax

You usually pay the sales tax when you transfer the title at the title bureau. Some dealers may include the sales tax along with the title transfer in house, saving you a trip to the DMV. As far as advertised prices go, I've never seen a dealer include sales tax. If you live in a state with sales tax, then expect to pay an extra 6.5 to 8%.

What other extra charges will there be besides the advertised price and tax (when buying from private seller)?

Sales tax, title transfer fee and registration fees. These are fees set by your state. and should always be associated with a car sale. Private sellers generally don't charge any "fees", other than their asking sales price. Dealerships may tack on additional fees just as a way of padding their profits, with some BS fees being more egregious than others. "Lot fees" (they're charging you for moving the vehicle around on their own lot), "delivery fees" (they're charging you the cost of the flat bed delivery from the auction lot they get their inventory from), "reconditioning fees" (they spent $15 on some kid to wax the car, so that's $300 to you), always look at the sales sheet before signing anything, and when you see tacked on BS fees like these, look the sales person dead in the eyes, spin on your heels and walk the hell out of the there.