In square foot calculations, I always round the result to the nearest $100. I feel at a $5,327 adjustment denotes a degree of accuracy that rarely exists. I don't make adjustments for items less then $500 in value. But that's just me. I don't impose my view on anyone else, but I do get a laugh when reviewing an appraial and seeing a $420 adjustment for a difference of 21 sf in GLA.
With FHA you are to round off. No problem, I agree with the logic behind requirement. But I have one UW that wants the "$420 adjustment for a difference of 21 sf in GLA". No problem there either, I'll give it to ya'....still doesn't change my Reconciliation.
For GLA adjustment, I round to the nearest $100 for anything $1,000 or higher. If the adjustment would be below $1,000, no adjustment at all. Occasionally for example I might make a $1,000 for one comparable, $2,000 for another instead of each adjustment based on per square foot. A buyer wouldn't--they might say to them selves, will this house has bigger rooms so I will offer $51,000 instead of $50,000 or this one has small rooms so my offer will be $49,000 instead of $50,000 (but then again the buyer might be making that $51,000 offer because they like the sound of the door bell). I also occasionally use what I call an "underwriter's adjustment" of $500--see underwriter I did make an adjustment for the subject's big porch versus the comparables small porch---it just doesn't have any effect on value which is $50,000 whether I adjust for that porch or not!
Concerning the message about adjusting for square footage under 100sf.......reminds me of a story. Using Wintotal to adjust a certain dollar amount per square foot, sometimes I forget to go back and change a small square foot difference to $0, which is my norm. The one time this was most evident was when I submitted 6 appraisals to the state board when I was applying for my license. I thought I'd gone over them pretty good to make sure I hadn't made any careless mistakes, but I guess I missed one. Most of the people in the room got a good laugh at my expense when one of the board members questioned how I could be so exact in my adjustments. On one of the appraisals I had a comp that differed from the subject by 1 sf, and there was the $15 adjustment sitting there. I was a little embarrassed, but just quickly remarked that "that's how exact I am, and anyone that good should definitely have a license." They got a laugh out of it, reminded me to double check my work, and gave me my license.
As posted above, I don't adjust for GLA differences under 100 feet .. measure to the nearest full foot, anyway! Round all adjustments within the grid to 100, and report final valuation rounded to $1,000 for values up to $100,000 and (generally) round to $5,000 for values greater .. unless (God forbid!) the range of indicated values is tighter than that ..