I don't believe in charge the whole amount onto the car. someone would have to pay for the 2-2.5% charges dealer is paying, that would be YOU.
I believe most dealer would take a deposit of up to approximately $3000, that is for in case your checks bounced, or finacing fell through. last time (3 days ago) I bought a car, I did not have my regular check book with me, so my wife wrote the dealer a check from an account with insufficient fund, we had to transfer money the next day. so dealer basically took my check based on my credit score. the $3000 I put on the credit is some kind of insurance I guess.