afni.nimh.nih.gov

NIFTI format files are converted to and from AFNI structures internally within 3dcalc and all other afni programs, so some rounding problems might happen. You can either use AFNI format for some of your other operations, or you can change the NIFTI header with nifti_tool as in the example here:

[afni.nimh.nih.gov]
<[afni.nimh.nih.gov];