Inner grid. Grid border is never on the outside.

main.js

	function set_grid_borders( ){

		var grid = $('.brand-grid');

		if( grid.length ){


			var grid_w = grid.width();
			var grid_h = grid.height();
			var grid_items = grid.find('.item');
			var item_width = grid_items.innerWidth();
			var item_height = grid_items.innerHeight();
			var cols = Math.round(grid_w/item_width);
			var rows = grid_items.length / cols;
			// If last row is not complete.
			if( rows % 1 != 0  ) {
				rows = Math.floor( rows ) + 1;
			} 
			var item_offset = rows * cols - grid_items.length;
			item_offset = cols - item_offset ;

			grid_items.css({
				'border':'1px solid #dadada',
				'border-top-color' : 'transparent',
				'border-left-color' : 'transparent'
			});
			grid.find('.item:nth-last-child(-n+'+item_offset+')').css({
				'border-bottom-color' : 'transparent'
			});

			grid.find('.item:nth-child('+cols+'n)').css({
				'border-right-color' : 'transparent'
			});
			if( rows == 1 ){
				grid.find('.item:last-child').css({
					'border-right-color' : 'transparent'
				});				
			}

		}
		console.log( 'columns:' + cols );
		console.log( 'rows:' + rows );
		console.log( 'offset:' + item_offset );

	}

	set_grid_borders( );

	$(window).resize(function(){
		set_grid_borders();
	});