Yes, NICKELS is a Scrabble word!

Letter values in Scrabble US: N 1, I 1, C 3, K 5, E 1, L 1, S 1.

Is it a valid word?

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

a hard malleable ductile silvery metallic element that is resistant to corrosion; used in alloys; occurs in pentlandite and smaltite and garnierite and millerite
a United States coin worth one twentieth of a dollar
five dollars worth of a drug

Also: atomic number 28, nickel note.

Not playable in Scrabble US: NI.