How Do I Get a Total of Taxes and added to Invoice Amount

How Do I Get a Total of Taxes and added to Invoice Amount

I am a very basic user and trying to "total" my columns in the Invoice.  Simple question.

I want to add the Tax amount for each item and have it added to the Total across the line.  Then I want to have the total tax added and displayed under the sub total.  

I am not a developer, but really am very technical.  Need help please!

S.No. Product Details Qty    Tax Product                                Total
${serialNumber} ${Products.Product Name} ${Products.Product Code}
${Invoices.Product Description}
${Invoices.Quantity}    ${Products.Tax} ${Invoices.Individual Tax}     ${Invoices.Total}
Sub Total ${Invoices.Sub Total}
Tax ${Invoices.Tax}
Adjustment ${Invoices.Adjustment}
Grand Total ${Invoices.Grand Tota