It would recalculate your rate to a one way rate - I'd tell them up front what you're doing so you're not surprised.

It has nothing to do with tags or ownership of cars - it has to do with the fact that one way rentals are normally more expensive (because one way renters have fewer alternatives so are willing to pay more) and they aren't going to let you get a one way rental for a cheaper price because you decided to lie about your return location.

That said, often intra California one way rentals are fairly reasonably priced, I've had great luck with National and Budget.