There is not an official end of year tie breaker in the Pick 'em pool settings. Many pool commissioners like to set a custom rule/post a message that the end of year tie breaker is the cumulative week tiebreakers.

You can find this by going to Reports -> Pool Week By Week. There you can mouse over the YTD column and header to see the values. You can then compare the values of those in each tied position and rank them that way (then post the leaderboard in a message on RYP or a text to the group members).