It wouldn't as easily in Canada then.
BUT..
Since you have a greater tax savings..

Since you save 15%. Have the buyer pay the 7%, pay him back the 7% and keep 8% (of the 15) for yourself OR offer to split the 8% w/ the buyer. Same thing (same % amount) as NY just a bit more complicated.

On a $100k car w/ a $80k trade in it's still $6400 in savings for you.

OR $3200 for you, $3200 for your buyer by splitting the savings .