look at these great signs.  now look at them again in more detail in order

GST is like VAT - ie a sales tax.  it would be great to go in to the shop and empty all the shelves in to a basket and see if you could really buy everything for $3 plus GST.

and look, you can save the 20 cents (about 10 pence) by buying 2 of everything (excluding other price umbrellas).  but if you've already bought everything once, can you buy it again ?

but his is where it gets very exciting.  They are selling SPECIAL $5 items as a test.  not sure whether that's $5 with or without GST.    But sorry, the $5 items do not apply 3 for $10.