Yup..I'd say put a 5 pound bag o sugar in a plastic shopping bag and see it it registers 5 pounds, give or take a few ounces.
After a few times using the scale though you'll get a more proper eye for weight. Also I suggest using a net or bag to weigh your fish. Not a big fan of placing the hook directly into the fish myself. With carp it is much more mandatory to use a weigh bag because of the sheer size, but it really only takes an extra moment to do and can greatly benefit all fish to have a little extra care.
For instance we usually net, tare the bag, transfer carp to bag and weigh..then release after the all important photo op
. Takes all of 1-2 minutes tops. Saves the fish's lips and/or gills if they decide to flip or flop on you..or worse if you drop em.