I Think As Long As You're A Minnow You Can Upvote Yourself Because Say You Have $0.01 Upvote And You Upvote Yourself 10 Times A Day For A Month :
$0.01 * 10 * 30=$3
So $3 Dollars In A Month Wouldn't Affect The Rewards Pool That Much But If You're A Whale You Should Definetly Help The Community And Upvote Others :)