So, let's look at the example.
Math.Round(1.5) //goes to 2, right?
Math.Round(2.5) //goes to 3, right? Wrong!
Go back to method definition on MSDN and read about method definition and return value once more - here.
public static decimal Round(
decimal d
)
"The integer nearest parameter d. If the fractional component of d is halfway between two integers, one of which is even and the other odd, then the even number is returned."
Okay, let's clarify rule.
Math.Round(1.5) //goes to 2
Math.Round(2.5) //goes to 2 !!
Very strange rule if you ask me.
Have a nice day.