If the charge was dismissed, it is not a conviction. These types of issues depend on the specific wording of the question. If the wording was...have you ever been arrested (or charged)...then your answer of NO would be incorrect, as you had been arrested and charged. If the question only listed ...have you ever been convicted...then your answer would be legally correct, as a dismissal is not a conviction. Try to get a copy of the disposition sheet from thje Court which this matter was in. You can then decide whether to take that to your company to show you did not mislead them, and you can use the disposition sheet to discuss your options with a lawyer. Once this is over, get your record expunged. Good luck.
This answer is provided solely for informational purposes, for you to use as a starting point when speaking directly with a lawyer in your State. I do not practice law in your State, and this answer does not constitute legal advice, create an attorney-client relationship, or constitute attorney advertising. I urge you to immediately contact an experienced criminal defense lawyer admitted to practice law in your State before you make any decisions about this case.