In order for the police to legally require a person to provide ID to them the person they're wanting ID from must be either committing a crime or be suspected of committing a crime.
If a police officer just walks up to you and asks for ID because someone called in about you then NO you do not have to ID yourself and you can tell them to just kick rocks.
There's no reason that you should ID yourself to the police officer unless you're either under arrest or committing a crime or being suspected of committing a crime.