Dr Bob,
I've read a lot of so called research that goes into the psuedo science of pricing, trying to determine the 'psychological' keys in the numbers. The bottom line is, nothing I've ever seen convinces me there is any magic solution.
The only method that has proven to me the relative value of one 'price' over another is actual sales results. Your customers are the ones who will tell you whether the $4 difference is a real difference or not. And quite frankly, at a $300 price tag, $4 shouldn't make any difference at all. (If the $4 is a serious consideration in your profit margin, you could tack it on as a processing or handling fee.)
Hope this helps.
Good Luck!
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