Can cash purchases track suppliers and GST?

[Scott Rowed]

Is there any easy way to track vendors and GST (Canada) when making cash 
purchases? For example I shop at Costco for the following items and pay 
cash:


Batteries....15.99 + 5% GST
USB flash drive....29.99 + 5% GST
Pizza for office party....13.00 (no GST)


At the end of the year I'd like to access a report on my purchases at 
Costco. Also, of course, I need to find out my total GST for the 
government reports.


In Gnucash, it seems that the best way I can do this is to open up a new 
bill to post in accounts payable, enter the data, then pay it after. 
This way it has the tax fields as well as linking the purchases to a 
specific vendor.


I used to use Quickbooks and there it was quite easy and fast.

Thanks.