You'd take the (Purchase price - trade in amount) + service charge = x amount. The x amount is how your sales tax will be determined. Then you have your tag/title registration cost approx $250.00 any leftover will be or should be refunded to you.
if the vehicle your using as a trade-in is still being paid for, and you have a balance after the trade-in amt (ex. outstanding bal $25000/trade in allowance $15000), then you'd add the $5000 along with tag/title/reg cost to x amount.
never heard the tire/battery tax, but have heard tire/battery admin type cost where dealer cost you to fill tires, charge battery and so on. a scam i think.
bill & jodi