When a volume is selected as the active volume in the volume module, setImageOrigin will be triggered in qMRMLVolumeInfoWidget.cxx:
QObject::connect(this->ImageOriginWidget, SIGNAL(coordinatesChanged(double)),
q, SLOT(setImageOrigin(double)));
It then sets Origin for the volume node. Currently the value got from Signal is not the original Origin, but the round-off value based on Slicer's precision (Application Settings->Units->Length).

E.g. The MR-head.nrrd from Sample Data originally has its space origin as (86.644897460937486,-133.92860412597656,116.78569793701172).
When it is opened in Volume module and then saved without any changes by user, its space origin is changed to (86.644999999999996,-133.929,116.78599999999999). This is based on the default precision: 3.

Volume Image Spacing has the same issue.

Expected behavior: qMRMLVolumeInfoWidget should only display the round off value, but it still uses the actual value to set volume node.

Discussion: assume the precision is the 3 (default one), z origin is then displayed as 116.786. If user changes it to 116.787, what value should Slicer use to update the volume node?
option 1) 116.787
option 2) 116.78669793701172 (= 116.78569793701172 + 0.001)