Well, first of all, your car is not new. Yes, it has very low miles, and it may even be in "like new" condition, but it is not new. (A new car has never been titled and comes with the full manufacturer's warranty from the date of purchase, and usually has less than 200 miles on it.) So please don't say that it is new. It's not.

Sales tax is applied on any car purchased - new or used - usually based on the tax laws in place where the car will be registered. Most states apply sales tax on the purchase of a used car. So whenever any selling prices or market values are quoted, it is always the amount of the purchase, not including tax, with any applicable sales taxes to be added on. You don't get to charge more because you already paid sales tax on it; most buyers will need to pay sales tax on top of the purchase price when they buy it from you.

It's hard to estimate a market value for a car with mileage this low, just because they are relatively rare - but I don't think it is worth as much as it was when it was new and came with the full four-year warranty (and remember, many folks bought their ITRs for $500-1000 under sticker). If it were my car, I would probably ask $23K and expect to negotiate down to a final selling price in the $21-22K range.