Yes, TOTALIZER is a Scrabble word!

Letter values in Scrabble US: T 1, O 1, T 1, A 1, L 1, I 1, Z 10, E 1, R 1.

Is it a valid word?

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

computer that registers bets and divides the total amount bet among those who won
a calculator that performs simple arithmetic functions

Also: pari-mutuel machine, adding machine.

Not playable in Scrabble US: TOTALISER.