So what I've done is teach about honesty often in my home. I teach with stories and examples. We talk about the natural consequences of dishonesty. Then when my kids tell a lie, I talk with them about it more....I ask them why they did it...and help them find a better way. This has been so much more successful than punishment when it comes to dishonesty. My kids really respond well to this and try really hard be honest.
Punishment just drives the behavior underground, it doesn't change it. Love and teaching will help them change self-destructive behavior. You will have to repeat yourself often...but I promise...it worked with my oldest daughter. She is now the most honest person I know. And so far, it's working with my other kids. Here is a link to some inspiring stories about honesty to share with children and teens. And here is a link to a great article about teaching honesty in your home.