This is really an interesting subject. And as many other things it really need some definitions I think... What do you mean by beeing dishonest, telling lies - little white lies or beeing an compulsive liar? It's a huge difference.
- But since Pisces is brought up in the mix, I wanted to state my oppinion. I'm Pisces, and a weird mixture of really really honest and feeling almost like I have no choice rather then lie sometimes.
Something in my chart make me very honest, I don't like lying about even the smallest things, everyday commonly things... I always tell the truth, I see no point in lying. Especially not in the effort to make me into something I'm not... If I have lied sometimes, I go around feeling guilty, and dishonest and like my whole integrity is broken...
But the times I can lie is when I think I might hurt somebodys feelings. Then I can lie even before I've given it a thought, or at least it's really difficult for me to be honest.
Like my aunt said (which also is a pisces with a lot of similarities to my chart): "I don't lie, unless I really have to!" And I know exactly what she means, beacuse when I can hurt someones feelings I can be enclined to feel that I have to lie...
Back to the topic... Mercury is the planet that rules thives, tricksters and jugglers... So I can see why it's a link to liars there. But I'm not sure about the moon in gemini part...
And I can recognise Neptune/Pisces and the foggyness, because I sometimes can loose track of what is true, when my feelings clouds everything up. I think a heavy Neptune influence can make you feel that this or that is true without seeing it clearly. Two very different reasons for lying...