Pence is the usual plural for an amount of money, although it's often replaced with "p" ("pee") when speaking informally.

Pennies means 1p coins, sometimes 2p coins too:

"Mum, I need sixty pence for the train, I've only got pennies and the machine doesn't take them."

"Pennies" without an amount means a small amount of money. "It's only pennies with the amount we use it."

(JK Rowling missed a trick. It should have been one bronze knut, two bronze knuts, and a price of four knets or something.)