In Recettear, when you're buying/selling, the tutorial gives you the base "range" of acceptable percents to offer to the customers. It seems that there's a magic number to put down in order to get the Near Pin bonus XP, and there's no real way to see this (understandably so, or else there'd be no real reward for doing so).
However, it seems exceedingly difficult to gauge this number when customers are both perfectly happy to buy things well below the given price range, and will typically pay the upper end of the spectrum as well. I'm pretty sure that I've hit Near Pin % bonuses on both high and low offers, though I could be wrong.
Does the Near Pin % fluctuate per transaction? Per customer type?