One guy buys the cigars, everyone yells "I WANT A 5er!" until all the cigars are spoken for.
The person who paid for the cigars figures out what 5 cigars plus shipping will cost the the people who wanted the 5ers will cost them. He lets them know how much they owe.
Then they either send the person who bought the cigars a Money Order or use an online service to pay. Then that person ships the 5ers out.

Happens all the time here. Most of the time with the following rules.
1) Guys who have never been in a trade or are brand new send their end first. This is sometimes waived if another older member vouches for the new member.
2) No one tries to make a profit on the cigars purchased. You paid 120 dollars for a box of 20 plus 8 dollars shipping? Then each 5er should cost 32 dollars plus shipping to the person receiving the 5er.
Its also a great way for a new member to show he is trust worthy. And if a newer guy doesn't want to take on the responsibility he can ask one of the older established members who are interested in some of the offered cigars if he will host the group buy or split.
Hope that answered your question.
Shawn