If you don't have the measured weights that sometimes come with scales or can be purchased individually, I'd recommend using a United States nickel/5 cent coin. They are supposedly an exact 5 g's each, and a Volt-100 scale requires 100 g's for recalibration. Therefore, you can recalibrate your scale using 20 nickels. I also use a Volt-100 and so far this has worked for me exactly; the most it's ever been off is .02 g, which is basically nothing.
What you do is remove your batteries, (I'd replace them with brand new ones if you have the option) then place the scale on a completely smooth, perfectly level, flat surface. Power the scale on, make sure it is reading 0.00, hold the M (mode) button until CAL comes on the screen, release the button for a quick second, then press it again one more time (quickly, don't hold this time), and then wait until "100.00 g" is flashing on the screen. Then you're going to place your 20 nickels on the scale as smoothly and with as little jostling or movement as possible. After a moment, the screen should read out "PASS". You then power the scale off (don't weigh anything before turning it off as it can possibly adjust the calibration you just set or weigh out heavily or light) and to test out your newly calibrated scale, turn it back on and weigh one nickel. It should be exactly 5 g's, with no more than a .02 digression in either direction if done properly. Good luck!
DigiWeigh 100 X...
on Jan 02, 2016