Note that this is a WI-specific reply.
The 5-day notice is specifically intended for unpaid rent, so you can't include late fees in the amount due. The good news is that you can be awarded reasonable late fees (generally $50 each or less) in court if the court knows about them. Below is a copy/paste from a notice I served this morning.
"This notice terminates your tenancy and requires you and anyone living with you to remove from the premises described in this notice on or before January 10, 2008 unless you pay the unpaid rent of $675, plus late fees, which was due on January 1, 2008."
Note two things. First, the notice acknowledges that there are unpaid late fees.
Second is the phrase "and anyone living with you". Address the notice to one tenant plus the legal latin phrase "et al" which interprets to 'and all others'. Example: John Smith, et al. Do that and include the previously-mentioned phrase in your notice and you will avoid the cost related to each additional named occupant. --70.92.x.xx