While selling a product, knowing well that it is a second grade product, you pass it off as first grade or high quality product even though you have no idea whether it is or not, is okay. It has been said that for a religious person, a Guru, a Saint and a teacher, speaking lies is absolutely prohibited; it doesn't happen anyway! For a king, a little bit of lies is acceptable, and for a trader, a little bit more lies is okay.
So a trader can speak that same amount of lies as there is salt in the food.