Well, I never heard of five player cribbage being played, but there's nothing to stop you :)

A good deal might be six cards each, and everyone discards one to the crib.

Five and six player cribbage can be played, but I found it's just too many people. The play may not even come back to you after you start. I've had better luck with splitting into two games. 2, 3, and 4 player games are fine.

5-player: Requires two boards and everybody plays cutthroat (individually). 5 cards to each player who discards one to the crib, except the dealer who only gets 4 cards and plays with what is dealt.

6-player: Requires a 3-player board and everybody plays partners. 5 cards to each player who discards one to the crib, except for the dealer and his partner who only gets 4 cards and plays with what is dealt.

For completeness:
3-player: Requires a 3-player board and everybody plays cutthroat (individually). 5 cards to each player who discards one to crib, and deal one more to the crib to make 4.

4-player: Requires a 2-player board and everybody plays partners/teams. 5 cards to each player who discards one to crib.