There are no* import taxes on any goods moved within the EU. That's a fundamental principle of the thing.
The fee to register a car for use on public road varies. It's very high in Denmark (120% of the value or something) but the place of manufacture doesn't affect that. Second hand imported cars still need to pay it.
* Exception is the duty paid on alcohol and cigarettes, depending how you define it.
Paying a tax on something you import from the EU which you don't pay if you buy in country is difficult to see as anything other than an import tax, no matter how it is named. See VRT in Ireland for example.
VRT is paid whether you buy a new vehicle from a manufacturer in Ireland or elsewhere in the EU. It's also paid if you buy a new vehicle from outside the EU, but in that case there will additionally be import taxes.
It might be that the administration is different (e.g. the large vehicle importer usually pays it, but you pay it yourself if you're buying some exotic Lotus direct from Britain).
Denmark has high taxes for registering a vehicle for public use to pay for road construction or maintenance and to discourage car use (or rather, to make the people using the roads pay their way).
The EU has import taxes on vehicles to protect its own vehicle industry, to both maintain that industry and the jobs within it.