Yes, PEGGING is a Scrabble word!

Letter values in Scrabble US: P 3, E 1, G 2, G 2, I 1, N 1, G 2.

Is it a valid word?

PEGGING is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

succeed in obtaining a position
pierce with a wooden pin or knock or thrust a wooden pin into
fasten or secure with a wooden pin
stabilize (the price of a commodity or an exchange rate) by legislation or market operations

Also: nail down, peg down.