No, You Can't.

If a Policeman has a good reason to search your car, your car will be searched whether you like it or not. If he does NOT have a good reason, he will ask you to provide one.

"Do you have any guns or drugs in the car?"
"Do you have anything dangerous or illegal in the car with you?"
"Do you have any weed in there?"

This is called "fishing" and it is Good Police Work. More felons than you could count have volunteered probable cause for a legitimate search by answering "Yes" when they didn't have to.

"Will you please step out of the car?"
"Can I have a quick look at your phone?"
"Will you open the trunk for me?"

The answer is always "No." If they can legally make you do it, they will TELL you, not ask you.

"I'll have to call in a K-9 unit then" is properly answered "Go ahead, I'll call my boss and tell him I'm going to be late, then I'll be reading my newspaper."

You do NOT have to give a COP your cell phone if he stops you for speeding. If you do, and he sticks it on the CellBrite UFED and rapes right through the passwords to download all your kiddie porn pics, underage sexting, deleted emails, etc. off your phone, you get to say BUBKIS about it in court because you volunteered to give it up.