Lying and the Price of Gas

I was having a conversation with the short people while pumping gas and they asked about the strange numbers on the sign in front of the station. I answered that it was the price of a gallon of gas and they asked why it always ended with 9/10ths of a cent. I explained that it was so that people seeing the sign would think they are paying $2.49 per gallon, but really paid $2.50. They got quite upset accusing all gas stations of lying. I said, grinning, that they were clearly advertising the true price, so how could it be lying? Their response (in different words) was that while they were telling the truth, they were saying it in a way they knew would be deceptive and it was that intention to use our psychology against us to make us believe something different than what they knew to be the case that made it lying. So, is it a lie?