What is the jail sentence for 5 pounds of cannabis?

This depends on the state, however with that amount of marijuana, you are also looking a distribution and trafficking potentially. The possession amount is a Felony (in all states), the amount is enough to distribute for sales and you could potentially trafficking the drug If you are caught in a car with it. Both are Felonies are well.

You are definitely looking at some prison time (not jail) If convicted.