I can see both sides on this one.
On the one hand it is superior service from the dealer that earns the tip.
On the other hand it is superior service from a restaurant server that earns the tip - but the support from the kitchen staff and restaurant staff all form part of that service experience - so there is an example where I believe tips should be shared.
I don't see a right or wrong way but if the dealer gets all of the tips, that should be offset by the amount of wages and benefits the others earn.
Tonyrob