Maybe nowhere. 

You can only include the tax (fee) based on the vehicle's value.  Different states treat the registration differently, so you'll need to know if (and how much) of the registration fee is deductible.

*IF* it is deductible, see line 5c.

https://www.irs.gov/instructions/i1040sca#en_US_2024_publink53061xd0e821