How do you gauge the Near Pin % of a transaction?

Searching around on the internet, I've found that apparently the best percentage to enter in order to get the most Near Pin bonuses is 104% if you want to get the most out of Near/Full Pin bonuses for Merchant/Customer experience levels. Each customer has a different percentage that they are willing to pay up to. For example, you may have noticed the Little Girl is an incredible cheapskate, while the Guild Master has a considerably larger budget.

Customer     Max Exp+rep     Max Profit    Max Exp+rep     Max Profit
              (selling)      (selling)       (buying)       (buying)
Girl         104%            112%(?)       70%             52%
Woman        104%            118%          70%             52% 
Old Man      104%            118%          70%             44%
Man          104%            127%          70%             39%
Guild Master 104%            127%          70%             41% 
Louie        104%            118%          70%             38% 
Charme       104%            127%          70%             47% 

Information is from this google doc, which has a more detailed collection of collected statistics overall about the game.