Short answer as mentioned by john1 already is that it should weigh 5.0g but has a tolerance of +/- .19g so 4.81-5.19g would be considered normally as being within tolerance, however weighing coins can potentially pay off over time.
Interesting that every modern nickel weighs 5.000 grams or 0.176 ounces including the 1942-1945 Nickels. Before the Jefferson nickels there were other series such as the Washington nickel, Shield nickel, Buffalo nickel and the Liberty Head V nickel. Each of these series also weigh exactly 5 grams other than the mentioned possible tolerance differences! So the nickels found in your change should all weigh 5 grams unless they have errors, damage or a different composition. The earliest nickels weighed much less than 5 grams. The first nickel ever produced was the " half disme". It was produced in 1792 and it weighs just 1.2 grams. Next came the Flowing Hair half dime (nickel) that weighs 1.34 grams. The Draped Bust and Capped Bust half dime series followed and they each weigh 1.35 grams. Starting in 1837 until the Coinage Act of 1873, the nickel went through changes so the weight wasn't consistent. In 1837 the Seated Liberty half dime was minted with a weight of 1.34 grams. In 1853 this coin's weight changed to 1.24 grams. It continued to be minted with a weight of 1.24 grams until the series ended in 1873.