Normal. If you want something to occupy your time and spend some money you could do a cooling system overhaul. Depending on the brand thermostat you get and the type of fan clutch it'll act different so you'll have something new to watch. Jokes aside, perform a close inspection to be sure you have no leaks and the coolant level is normal. Replace the cap, it is too cheap not too and just watch for larger spikes, much larger spikes. Minor fluctuations are exactly how the cooling system is designed to work.