and fix negative rounding code, which results in changing tet
of from -996 to -1002 which is closer to the original -1000

Change-Id: Ie992e61bf4d14d0cd4194e773479feba96b6d68e
Reviewed-on: https://gerrit.libreoffice.org/51576Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>