If your current or prospective employer does not ask about your criminal record, why would you ever volunteer such information? How would the unprompted disclosure of such information enhance your prospects of being hired or retaining employment?
If an employer asks, it behooves you to tell the truth. (FWIW, it seems 90% or more of employment applications inquire about criminal convictions.) If an employer does not ask, there would appear few, if any, circumstances in which voluntary self-disclosure would appear warranted or prudent.