Try doing that in TX and you’ll be sitting there for a while because normal people will answer that question unless they have attitudes or are trying to hide something. That is standard question to determine if you could possibly be a drug trafficker. If refuse to answer then you will continue being detained until the cop can complete a full history/background check on you. He will also probably order you to step out of the car.
Remember, respect is earned and respect begets respect. If you have attitude then don’t be surprised if the cop returns the favor. You’re not required to be respectful, but neither is the cop according to the law.
It is none of their business where I am going. None at all. The answer would not give any indication of drug trafficking. The whole war on drugs is just a money maker for the police, anyway.