Subtotal incorrect

So far I have ran quite a few test orders ok - and I have had orders places (just one with a problem that I figured out with the forum's help). I don't seem to find any problem like this in the search on the forum :unsure:

Just had an order with a lot of small $$ amount items (ie $0.30-1.99 each) ordering multiple of most items.

This is what displays
Sub-Total: $33.18
(Shipping for ): $12.00
GST: $2.05 Total: $47.23

Our GST is 6% - so based on the subtotal it is too much....BUT if you add up all the items from the TOTAL(INC) column the subtotal is $34.78 - which makes the GST correct.

It's not a big deal since I am getting paid the proper amount BUT it doesn't look good for customers placing an order KWIM.

TIA

Anyone? I don't know why I said I was paid the proper amount...this order is a little off - not a huge deal but if more orders are ...I can't afford to have the totals wrong especially on small $$ amount items

Ok - I 'kinda' figured it out. It was something to do with the cart upsell add-on. So I just deleted it for now and will search what's the problem later. Now the total etc shows correctly.