minor library optimization to Numeric.roundTo
minor library optimization to Numeric.roundTo

Ignore-this: a8ddb9ddd8d55f7ebfcaae50b4d8b871

darcs-hash:4320028d7c340cb22b7c49fe41c562c0d3942a82

dpwright/jhc,dpwright/jhc,dpwright/jhc,dpwright/jhc