$(function() {

    var values = [0, 50, 90, 330, 500];

    var slider = $("#slider").slider({

        orientation: 'horizontal',

        min: values[0],

        max: values[values.length - 1],

        value: values[0],

​

        slide: function(event, ui) {

            var includeLeft = event.keyCode != $.ui.keyCode.RIGHT;

            var includeRight = event.keyCode != $.ui.keyCode.LEFT;

            var value = findNearest(includeLeft, includeRight, ui.value);

            slider.slider('value', value);

            $("#amount").val('$' + slider.slider('value'));                      

            return false;

        }

    });

    function findNearest(includeLeft, includeRight, value) {

        var nearest = null;

        var diff = null;

        for (var i = 0; i < values.length; i++) {

            if ((includeLeft && values[i] <= value) || (includeRight && values[i] >= value)) {

                var newDiff = Math.abs(value - values[i]);

                if (diff == null || newDiff < diff) {

                    nearest = values[i];

                    diff = newDiff;

                }

            }

        }

        return nearest;

    }

$("#amount").val('$' + slider.slider('value'));

});