Price per unit weight - 3 decimal places

Hello,

That display is made in the view "product / listing_price".
But because the price is displayed via the currency helper (and his "format" function) ; the round is made directly in that function depending the settings of your currency.
It means that if you edit your currency to have more digits, it will impact every prices everything in your website.
So if you want to change the way that price is displayed ; you'll need some custom code to display the price manually and have your own rounding.

Regards,