I'd cover the 10yrs...they're going to get a 10 yr history in detail from the background check anyway. I got asked following the background check about a company I worked for. In my given history, I told them I worked for the company during a time frame. That company changed names after I left and it indeed showed on the background check that I worked for them but the check said nothing about the name change. Therefore, the way they saw it, I worked for two companies during that time when they compared what I told them and what the check uncovered. It was clarified with a simple phone call and a guy I know who still worked there made me a notarized letter of time I worked there and that they changed names but were the same company. I faxed HR that letter and got a call two days later with a thanks for the clarification and a class date.

Just tell them everything, it prevents them ever having the thought that you're hiding anything and shows you're straight up.