Bug 13321: Fix unitprice rounding

Bug 13321: Fix unitprice rounding

We need to display the rounded value, but insert the exact value.
The unit price can be change on receiving, so the input value can be
modified.
But if it's not, we must insert the exact (not rounded) unit price,
which is the ecost value.

Signed-off-by: Laurence Rault <laurence.rault@biblibre.com>
Signed-off-by: Francois Charbonnier <francois.charbonnier@inlibro.com>
Signed-off-by: Sonia Bouis <sonia.bouis@univ-lyon3.fr>
Signed-off-by: Sonia Bouis <koha@univ-lyon3.fr>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>