Vehicle tax details are available online in TamilNadu. Before going to the Dealers , just be aware of the tax details in the following link.
Tax details are classifed based on the weight of the vehicles.
The vehicles tax details can be viewed in the following screen
Goods Carriages - Lorries ,Light Goods Vehicle,National Permit Vehicle ,Articulated vehicle http://www.tn.gov.in/sta/t1.html
Contract Carriages-Omni Bus,Maxi Cab Vehicle,Ordinary and Tourist Motor Cab,Autorickshaw tax details below
http://www.tn.gov.in/sta/t2.html
Stage Carriages(per seat per quarter)- Town Service,Mofussil Service,Express Service,Mini Bus Tax details below
http://www.tn.gov.in/sta/t3.html
Private Service Vehicles - Educational Institution Bus tax details below
http://www.tn.gov.in/sta/t4.html
Non Transport Vehicles
Motor Cars, JEEPs, Etc. (Annual Tax) - http://www.tn.gov.in/sta/t7.html
Life Time Tax - http://www.tn.gov.in/sta/t8.html
Rig,Tractor,Construction equipment - http://www.tn.gov.in/sta/t9.html