SO Fiddle

HTML

<table id="tabela" class="table table-striped table-bordered dt-responsive nowrap">
                                        <thead>
                                            <tr>
                                                <th>Seq</th>
                                                <th>Produto</th>
                                                <th>Componente</th>
                                                <th>Qtde </th>
                                                <th>Valor unit </th>
                                                <th class="calcular">Valor Total </th>
                                                <th>Percentual </th>
                                                <th>indice </th>
                                                <th>Observação </th>
                                                <th>Data</th>
                                                <th></th>
                                            </tr>
                                        </thead>
                                        <tbody id="tabelaItem" style="border-spacing: 8px; border-collapse: separate">
                                        </tbody>
</table>

CSS

.total {
}

JavaScript

$(function () {
        var tbl = $('#tbl_a');
        tbl.find('tr').each(function () {
            // $this = this;
            $(this).find('input[type=text]').bind("keyup", function () {
                calculateSum();
            });
        });

        function calculateSum() {
            var tbl = $('#tbl_a');
            tbl.find('tr').each(function () {
                var sum = 0;
                $(this).find('input[type=text]').not('.total').each(function () {
                    if (!isNaN(this.value) && this.value.length != 0) {
                        sum += parseFloat(this.value);
                    }
                });

                $(this).find('.total').val(sum.toFixed(2));
            });
        }
    });