I'm surprised that former LEO's on here would advise allowing the officer to inspect inside my vehicle without the proper warrant/suspicion.
Every policeman I've known tells me the proper answer to "do you mind if I take a look inside" is "yes I do mind, and I'll wait here till you have the warrant".
There is a well known yootoob about this, in which the lawyer and policeman agree that there is NOTHING positive for you to come from such a search, only potential problems.
Now, if he says he will come in anyway after my refusal, I'm not going to stand in front of him. But he knows my position.
To not honor the Constitution dishonors those who defended it at great cost.