miniShop2.Utils = {
        empty: function (val) {
            return (typeof(val) == 'undefined' || val == 0 || val === null || val === false || (typeof(val) == 'string' && val.replace(/\s+/g, '') == '') || (typeof(val) == 'object' && val.length == 0));
        },
        formatPrice: function (price) {
            var pf = miniShop2Config.price_format;
            price = this.number_format(price, pf[0], pf[1], pf[2]);

            if (miniShop2Config.price_format_no_zeros && pf[0] > 0) {
                price = price.replace(/(0+)$/, '');
                price = price.replace(/[^0-9]$/, '');
            }

            return price;
        },

<field key="price" dbtype="decimal" precision="12,2" phptype="float" null="true" default="0"/>

выставил тип decimal(12,3) и в настройках прописал формат.

miniShop2.Callbacks.Cart.add.response.success = function() {    
    $( "#shopModal" ).show();    
    $('.close').click(function(){
           $('#shopModal').hide();
        });    
    $(document).click(function(event) {
        if ($(event.target).closest(".modal-dialog").length) return;
        $("#shopModal").hide("slow");
        event.stopPropagation();
      });
    }