The life of an OCP librarian

I think all OCP people have some sort of obsession with numbers, even though it varies by person.  One of my weird ones is with checks and bills.  I love to write even numbers on checks and for bills.  When I go to a restaurant, I almost always try to make the check with the tip as even as possible ($6.29 is annoying, $6.50 is good, and $6 is perfect!).  When I write checks to pay bills like the electric bill ($79.84 or something), I always want to write the check for $80.  I have no idea where this obsession comes from, except maybe being left over from the days where my checkbook was actually in a book and not on the computer.