Let me add a little perspective first. When a cop pulls you over, it is essentially his/her job to collect enough evidence to convict you of something. They work in coordination with prosecutors, and prosecutors typically need evidence to convict someone of an offense. You may be aware of the phrase in the Miranda warning that reads "anything you say can and will be used against you in a court of law." It is important that you see that it only says AGAINST you. Evidence will never be provided that might be used for you.

So how does this relate to the 5th Amendment, you ask? The part that reads, "No person shall be held to answer for...nor shall be compelled in any criminal case to be a witness against himself," is the clause that would apply if you're being pulled over. Due to the 5th Amendment, you have no requirement to be a witness against yourself because you would be providing evidence that will be used against you.

For instance, suppose a police officer asks you how fast you were going in a speeding stop. If you know you were doing 15 over, but instead try to say you were only doing 5 over, not only have you just admitted to breaking the law, but you've also attempted to obstruct justice. Perhaps this was a bad example, but there are literally no scenarios where it pays to talk to the police.