Edit in JSFiddle

$(function(){
  var $slider = $('.slider')
    , slider_width = 0
    , $slider_inner = $slider.children().first()
    , $elements = $slider_inner.children('.element')
    , elements_count = $elements.length
    , element_width = $elements.first().width()
    , element_margin = 0
    , elements_fit = 0
    , visible_width = 0

  function onResize() {
    slider_width = $slider.width()
    elements_fit = Math.floor(slider_width/element_width)

    // we have a limited number of elements
    if (elements_fit > elements_count) {
      elements_fit = elements_count
    }
    // we need only odd number
    if (elements_fit % 2 === 0) {
      elements_fit -= 1
    }

    // find element margin for balancing
    element_margin = Math.ceil((slider_width - (element_width * elements_fit))/(elements_fit * 2))

    visible_width = (element_width + element_margin * 2) * elements_fit
    // set container width * 1.5 to fit clonned elements when scroll
    $slider_inner.width(Math.ceil(visible_width * 1.5))
    // add margins
    $elements.css({'margin-left': element_margin + 'px', 'margin-right': element_margin + 'px'})
  }

  onResize()

  $(window).on('resize', onResize)
})