Need to be able to add tax to invoices

In BC Canada therapists still need to charge GST and so there needs to be a way to add tax to invoices. I know we can currently set session rates to include tax but it is important for this amount to be tracked separately for clients and practitioners. (And if I have to just include it in the session cost there needs to be able to be decimals. It totally messes up my claculations for tax owed if I have to round the session rate with tax to the nearest dollar.)