You have three options, 1. Void the round entirely and restart. 2. Give the round to the team with the advantage. 3. Play the 3v5 or 5v3.
The 3rd option is retarded because its basically exactly the same as voiding the round except you are playing a COMPLETELY DIFFERENT match in a completely different style and format. It makes zero sense, besides none of the energy or real time play can be carried on if that happens and it would be played COMPLETELY DIFFERENTLY to how a 3v5 would be played in a crazy fast open melee situation towards an end of a round.
1st option is the most sensible as its not biased to either team, 2nd and 3rd options means you HAVE to be biased to one team, you have to give 1 team the round or an advantage which simply isn't fair.
edit: It's extremely unfortunate for the team who had the previous advantage but as we know in NW there is absolutely nothing GUARANTEEING them victory in a 5v3. Either way its the fault of the admin team (shadey) for not setting the point limit correctly TWICE.