ok.. It all depends on what you do. Here are NYS rules:
1. If you buy the car and the dealership will/able to register for you, then they will collect NY tax 8.25% and you can roll it into your loan.

2. If you will be registering the car yourself, then usually the dealer will not charge you any state tax. Therefore, your loan will reflect as such. When you arrive at the NY DMV, you would have to pay the state tax via check, CCard, MO

3. If for somereason the dealership charged you CT tax, you can get that portion roll on your loan. When you arrived at NY, you have fill out DT-803or 804 which allows you to pay the difference. IE..you pay CT tax...6% and NY tax 8%, then you would be charged 2% at DMV

4. If your military, then you can fill out a tax deferment and not pay any NY sales tax at all until you get out of the military and return to NY.

 

I purchased my car from a dude in oregon private party. they cannot collect sales tax if you purchase private party. you will then pay sales tax out of pocket in the state that you title/register the car in. in my case, idaho collected their 6%. I sold my old eclipse prior to this to a kid in minnesota, but his dad paid for it with a wire transfer from north dakota. I did not collect sales tax and you shouldn't if selling a used car. the dmv will collect at time of title/registration based on whatever your state has. in idaho, it's based off the bill of sale price. if you finance the car off a dealership, they should not collect tax either if you are taking out of state or titling out of state. tax shouldn't be paid until you title.
a friend of mine has purchased 3 new ford f-350 diesel trucks here in idaho, registered it to his vacant lot in oregon(has 0% sales tax) and idaho cannot collect sales tax since the title/registration and plates are all out of state, but he did purchase them in idaho.
as far as putting down a phoney price, I have seen/done this in the past but you have to be careful. dmv will begin to ask questions if you are registering an 03 that you paid $1 for. Idaho even has something to do with "gifting" a car and it is much harder now. I had to get a form filled out when my grandma gave me my grandpa's 78 ford. they wouldn't take a bill of sale as a gift. had to have a form filled out with relationship, all addresses and phone#'s, etc...

there are a lot of ways around it, but the more people that screw the system, the more our taxes are going up to make up for lost ground

 

Yeah I guess it can work both ways.... What if I was buying a fully built 91 AWD eclipse or talon that runs 9's for $20k. The blue book on it would be like $1-2k. Am I going to pay sales tax on $20k? I think the only thing that matters in this state is what price the seller writes on the title when he hands it over to you... Then you bring that title to the dmv, they take it and charge you salex tax, and print you out a new title with your name on it, and blank spaces on the back for whoever you sell the car to next. And the cycle continues. I dunno, on whatever Evo I get, I'm making the seller write atelast 1/2 of the actual selling price on the title. Salex tax blowz.