The ninth commandment, according to Rabbi Marc Gellman and Monsignor Thomas Hartman in their excellent book, How Do You Spell God?, is "Tell the Truth!" How simple can you get? Tell the truth. Not tell most of the truth or touch on the truth or vaguely reference the truth, but tell the truth.
In a court of law, one does not hear the witness say, "I do solemnly swear to kinda, sorta, maybe tell some of the truth." We want the truth, the whole truth, and nothing but the truth, so help me God (but we'll get to the religion later).
Many people say they don't lie, but...gossip is lies, or partial truths. The juicier the gossip, the faster it spreads, and once a rumor is started, there is no stopping it and no taking it back. Most of us have been victims of gossip or outright lies at some point in our lives. Nothing stings so much as a false accusation.
Cheating on taxes is a lie. You can pay for that one.
Breaking a promise is a lie (unless the promise was damaging). Don't make a promise lightly just to appease someone. It is far better to say you'll try to do something (even when it's a good thing to do) than it is to make a promise you may not keep (or have no intention of keeping).
Little lies, white lies, fibs, story enhancements...more often than not, they come back to haunt us. Once we're caught in a lie, trust is gone, and it's really hard to get that back.
We do not, however, have to give the hurtful truth. We shouldn't volunteer that someone's dress looks horrible on her, or that the wonderful casserole Aunt Melva made really isn't wonderful. Aromatic might describe it, but not wonderful. We don't have to tell Aunt Melva her casserole could probably strip paint. We can find a nice way of saying things. We should aim not to be hurtful.
As Paul says in his first letter to the Corinthians, (1 Corinthians 10:23): "All things are lawful," but not all things are beneficial. "All things are lawful," but not all things build up.
As a wise person once said, "If you can't be kind, at least have the decency to be vague." We need to be a truthful people, but we also need to remember to be loving and supportive of our brothers and sisters in Christ, and our brothers and sisters in the world. We may be the only Bible they ever read.
What do you want that Bible to say?