[plt-scheme] mzscheme iota() results differ slightly from spec

According to http://srfi.schemers.org/srfi-1/srfi-1.html#iota

The following should happen:

(iota 5 0 -0.1) => (0 -0.1 -0.2 -0.3 -0.4)

However, under the Cygwin version of MzScheme, I get this:

Welcome to MzScheme version 206, Copyright (c) 2004 PLT Scheme, Inc.
> (require (lib "1.ss" "srfi"))
> 
> (iota 5 0 -0.1)
(-2.7755575615628914e-017 -0.10000000000000003 -0.20000000000000004 -0.30000000000000004 -0.4)
> 

What should I have done in addition to loading the SRFI-1 library in order to get the same results?