[racket] Possible bug with sine and cosine (simple floating-point issue?)

I'm running the Windows build of 5.0.2 on 32bit Windows 7 and I've run into
the following issues with sine and cosine. Here is a paste of my interaction
with Racket:
> (inexact->exact (sin 0))
0 ; fine
> (inexact->exact (cos 0))
1 ; fine
> (inexact->exact (sin (/ pi 2)))
1 ; fine
> (inexact->exact (cos  (/ pi 2)))
0.0000000000000000612323399... ; should be 0
> (inexact->exact (sin pi))
0.0000000000000001224646799... ; should be 0
> (inexact->exact (cos pi))
-1 ; fine
> (inexact->exact (sin (* 3 (/ pi 2))))
-1 ; fine
> (inexact->exact (cos (* 3 (/ pi 2))))
-0.0000000000000001836970198... ; should be 0
> (inexact->exact (sin (* 2 pi)))
-0.0000000000000002449293598... ; should be 0
> (inexact->exact (cos (* 2 pi)))
1

Granted it is a very small amount to be off by and I doubt it's throwing off
my answers at all (working on exercise 27.1.4) just thought you should be
aware of it.
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