Tact is good ("does my bum...") Outright lying surely shouldn't be necessary in a healthy relationship. I wouldn't lie to the children either, though obviously some things have to be, shall we say, glossed over, depending on the age and sensitivity of the child. They get enough of a shock the day they realise their parents don't know everything. It would be hard on them indeed if they were to find out their parents had often lied through their teeth as well. No, I didn't tell them Santa Claus really comes down the chimney! Someone else did that, at school probably, and I had to do a lot of reassuring DS1 who was quite alarmed at the thought of a strange man breaking into our house while we were asleep. (DS3 insisted on believing Santa was literally true until he was about 8. I was a little worried about him.)
I can think of two occasions in her whole life when I know my mother was less than honest: one was a weeny white lie about the ingredients in dinner, the other was a huge great cover-up about her terminal illness. Even then I could tell because she was clearly uncomfortable with what she was saying. People trusted her and they were right to do so. She would never tell an untruth that hurt or damaged anyone else. On the other hand she wouldn't tell a truth that would hurt or damage anyone else either. I used to get family and friends lecturing me on how lovely my mother was; er thank you, I had noticed! (And one uncle who told me she was a lousy housekeeper. That said a lot more about him than it did about her tbh.)
My father, on the other hand, always sounded honest but sometimes he just made it up as he went along. More often he'd avoid uncomfortable truth-telling with a joke though. He was very much The Man Of The House (more of this on another day and another thread, probably) but he wouldn't want my mother to catch him lying - some things were zero tolerance.
XH wouldn't know the truth if it bit him. He would often accuse me of lying, I suspect to annoy me because he knew I value honesty very highly, but it could have just been paranoia and/or projection. No. 6,395 in a series of "why he is XH"!