Funny or smart Rounding Adjustment issue in Sales Invoice!

Funny and weird rounding adjustment issue experienced on Sales Invoice (same might be also on the SO & PO too !)

I simply just created two different Sales Invoice, with the following amount :

  1. Set amount to 500.50, it rounds to 500 (Rounding Adjustment (INR) = -0.50)

  2. for another invoice set the amount to 499.50, it again rounds to 500, here interestingly (Rounding Adjustment (INR) is positive +0.50)

It is kind of a smart Adjustment, but does not have a constant behavior, it smartly sometimes rounds up or down based on the total.

settings info: Under System setting, Float Precision is set as 3

Any idea on this, is this intentional or an issue?!