It's the last ball of the over. The ball hits the helmet kept behind the keeper. 5 runs will be awarded, but my question here is, will the same batsman face the first ball of the next over?
No - penalty runs don't cause a change in the on-strike batsman, just as a no ball or wide doesn't. The normal change of bowling end then happens, and the non striker then becomes the on-strike batsman.
This is covered (or more precisely, not covered) by Law 41(3) which makes no mention of the batsmen changing ends due to the award of penalty runs.