Sales tax
Some states offer a sales-tax credit or refund tied to a totaled vehicle when you register a replacement — essentially crediting tax already paid on the vehicle you lost. This isn't automatic everywhere, and where it exists, it usually requires specific paperwork and a time window to claim it.
Title transfer and salvage fees
If you surrender the vehicle, the insurer typically handles the title transfer as part of the settlement. If you keep the vehicle, you'll likely handle a title-branding process yourself, which can carry its own state fees.
Registration
Canceling registration on the totaled vehicle (if you no longer have it) and registering a replacement are both handled through your state's motor vehicle agency, and requirements — including any refund for unused registration — differ by state.