WCS Server does not return data at the correct resolution

[ben.tuttle@…]

If starting with a 30 arcsec (0.00833333 degrees) data set in a mapserver WCS,
when I make a WCS request using resx=0.00833333 and resy=0.00833333 the output
image returned by mapserver does not register correctly and gdalinfo returns
Pixel Size = (0.00836820,-0.00836820). The new pixel size can vary slightly
based on the bounding box of the request. The main point is that the output
image (we are using geotiff) is not the same resolution as the request. 

Example:
http://www.ngdc.noaa.gov/eog/maps/test5.php?SERVICE=WCS&REQUEST=GetCoverage&Coverage=vis_mosaic&STYLES=&CRS=EPSG:4326&BBOX=-125,30,-115,40&resx=0.00833333&resy=0.00833333&Format=geotiff
the data comes back as  0.00834028,-0.00834028 instead of
0.00833333,-0.00833333 (the native resolution of the data is
0.00833333,-0.00833333). Additionally the given bounding box actually
covers an area 1201px by 1201px in the data. However, the returned
image is 1200px by 1200px. If compared to the original data one can
see that mapserver has resampled the returned image to fit the area
which is 1201 by 1201 into an image that is 1200 by 1200, which
explains the change in the resolution. It seems to me that this may
not be the the desired behaviour for WCS. I would expect to get my data
back at the same resolution requested.