Rust #fmt doesn't round floats?

knucleotide.diff

$ diff -u knucleotide-output.txt <(rustx knucleotide.rs < knucleotide-input.txt)
--- knucleotide-output.txt	2012-05-30 02:33:06.912688859 -0700
+++ /dev/fd/63	2012-06-01 01:39:47.330695330 -0700
@@ -1,19 +1,19 @@
 A 30.279
-T 30.113
+T 30.112
 G 19.835
-C 19.773
+C 19.772
 
-AA 9.161
-AT 9.138
+AA 9.160
+AT 9.137
 TA 9.108
 TT 9.060
 CA 6.014
 GA 5.996
-AG 5.993
+AG 5.992
 AC 5.988
 TG 5.987
 GT 5.967
-TC 5.958
+TC 5.957
 CT 5.948
 GG 3.944
 GC 3.928