Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 17484)
+++ wp-includes/media.php	(working copy)
@@ -818,7 +818,7 @@
 	$itemtag = tag_escape($itemtag);
 	$captiontag = tag_escape($captiontag);
 	$columns = intval($columns);
-	$itemwidth = $columns > 0 ? floor(100/$columns) : 100;
+	$itemwidth = $columns > 0 ? round(100/$columns,2) : 100;
 	$float = is_rtl() ? 'right' : 'left';
 
 	$selector = "gallery-{$instance}";
@@ -1405,4 +1405,4 @@
 	require_once( ABSPATH . WPINC . '/class-oembed.php' );
 	$oembed = _wp_oembed_get_object();
 	$oembed->providers[$format] = array( $provider, $regex );
-}
\ No newline at end of file
+}