[Koha] Calculating fines?

[George Adams]

Hello.  In testing Koha 3.0 alpha, I have a user who has checked out a book which is now overdue by 3 weeks.  According to the overdue/fine rules, he should be getting charged $0.25/day in overdue
fines, but when he logs into his account it shows the overdue book in red but displays "No" in the fines column.

Looking for some documentation, I stumbled across a mention of a cron job to calculate fines, at least back in Koha 2.2.x .  Assuming it's still done that way, I hunted around the Koha tree and found
these likely candidates:

    <koharoot>/bin/fines.pl
    <koharoot>/bin/fines2.pl
    <koharoot>/bin/cronjobs/fines2.pl
    <koharoot>/bin/cronjobs/fines-sanop.pl

My questions are:

1) All 4 of these scripts say "This script is meant to be run nightly out of cron".  Which of these should I actually setup to run nightly?

2) Why is a cronjob even necessary?  i.e. why can't Koha look at today's date and the books' due dates, then calculate on the fly what the overdue fines are whenever the patron or librarian pulls up
a record within the OPAC?

Thanks.