round() and negative digits

Carl Witthoft's serendipitous discovery is a nice example
of how secrets can be guessed by wondering "what if ... ?".
So probably you don;t need to tell the secrets.

Taking the "negative digits" to their logical extreme:

   round(654.321,2)
   # [1] 654.32
   round(654.321,1)
   # [1] 654.3
   round(654.321,0)
   # [1] 654
   round(654.321,-1)
   # [1] 650
   round(654.321,-2)
   # [1] 700
   round(654.321,-3)
   # [1] 1000
   round(654.321,-4)
   # [1] 0

which is what you'd logically expect (but is it what you
would intuitively expect?).