update custom cart - change so we are charging on shipping amount also

have a custom cart that is written in ASP Classic - using Ajax with Javascript to calculate the tax amount and totals for the cart. We found out that we are supposed to be charging tax on the shipping also - so we need a very minor change to the code so that it adds the shipping to the sub total before calculating the tax and change the total calculation so that it matches the calculation. Should be easy for someone that is really good in Javascript. No access to server - I will provide the appropriate files and you will update and send back.