PST on Expenses

I am from Vancouver BC area. We pay 7% PST on expenses. I am trying to enable tax calculations on our Sage 300 which are currently disabled on our AP System. When I do that, system is posting expense and applicable tax as two separate line items in the expense account. For example, if I post a purchase of $112 of office supplies, Office supplies expense will get two lines one for $100 and another for $7, instead $107 as one line. Is that common in Sage 300? I don't see that in either Sage 50 or QB? 

Thank you for any help / suggestions

Raju Nanduri