Index: wp-content/themes/twentytwelve/rtl.css
===================================================================
--- wp-content/themes/twentytwelve/rtl.css	(revision 22580)
+++ wp-content/themes/twentytwelve/rtl.css	(working copy)
@@ -41,6 +41,15 @@
 	float: left;
 	text-align: left;
 }
+/* IE Navigation */
+.ie .main-navigation ul.nav-menu {
+	text-align: right;
+}
+.ie .main-navigation ul li ul li,
+.ie .main-navigation ul li ul li ul li {
+	margin-left: 2.85714rem;
+	margin-right: auto;
+}
 
 /* Author profiles */
 .author-avatar {