ok yeah i can't find any users manual type thing on it...

but on that site they have them for sale for 15.00... so if you can't get it to recalibrate, could always get a new one i suppose?

"A US cent weighs exactly 2.5 g, while the nickel weighs exactly 5 g."

Commonly used metric system units, symbols, and prefixes

so you'd need 20 nickels for 100 grams...