Tolls inside Seattle’s new Highway 99 tunnel would peak at $2.25 during weekday afternoons, under a plan the state endorsed Tuesday. The cost will vary by time of day, with a proposed minimum of $1 overnights and weekends. Drivers can use the tunnel for free the first few months, after it opens to traffic this fall. Members of the volunteer Washington State Transportation Commission voted Tuesday to publish the proposal for one last round of citizen comment, before deciding final rates in October.