Bug 27079: Floating point comparison correction

Bug 27079: Floating point comparison correction

We cannot compare calculated values directly as those calculations may
have introduced floating point differences.  We have the
Koha::Number::Price->round function to consistently round the floating
point number to a decimal with 2 points precission for comparison.

Test plan
1/ Set a circ rule to have a .15 per day fine and enable finesMode
syspref.
2/ Issue an item of this type to a borrower (making it 12 days overdue
   by setting the due date to 12 days in the past)
3/ Run the fines job:
4/ Pay the fine for the patron
5/ Check in the item
6/ Note that the patron does not have an 'Overpayment refund' of $0.00

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Bug 27079: (QA follow-up) Round both sides for clarity

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>