It is not possible to judge 5 lbs of pressure difference in your tires. Lower sidewall profile tires, due to their stiff construction, make it even more difficult.
It is normal for tires to lose, on the average, 2 to 3 lbs per month. Add in the cold temps and you can see why any car newer than 2008 is required by law to have tire pressure sensors.
I would guarantee that if you randomly checked tires pressures, 2/3 of the cars would have at least one under-inflated tire. Check them now.