I don't lock because of 'value' in the bag (or lack thereof - LOL) but because I don't want the zippers coming open. Seen it happen too many times!
I used to use zip ties and that was fine. (I even used a wire/paper twist tie a couple of times and that worked well too.) Then DH got me a set of TSA locks for Christmas a few years ago and I use them now.
Using the zip ties, I was inspected once. They put a loop type fastener in place of it. I've never been inspected when using the TSA approved locks. (My locks have an indicator on them that tells me if TSA opened them and it's never been activated.)
That said, I almost never check my bags going to my destination, but I frequently do going home. (If the bag gets lost/delayed going somewhere, I'm S.O.L. But if it gets lost when I'm going home - well, I have more clothes etc there!)