I'd log it, then one day when you're going back through your logs for the heck of it, you'll have that nice little notation in your book. Half of my flights for the maint. department are .5 or less, so they add up for me. I once logged a .3 one lap in the pattern, weather came down on us. Jus the small things, there's nothing that says you "have" to, but honestly, it's your logbook and your experience.