Bug 27801: Fix javascript price calculations

Bug 27801: Fix javascript price calculations

This patch ensures we're formatting the price values consistently for
the table total and the amount to pay input field.

Test plan
1) Add an item to charge at 0.10.
2) Add this same item 8 or 9 times (Do not use the 'quantity')
3) Note that the table total and the 'Amount paid' values do not match
4) Apply the patch and repeat the above steps.. the values should now
   match.

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 7e72a7dde5a73ed6177b321d29fca0df13f08f2c)

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
(cherry picked from commit 9e16f33b37aaf107ff3293df0cd3da5f94563c81)
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>