1. If coke costs 98 cents a can and I buy 10 cans, do I round up the 98 cents to $1 first?

No, you would be paying far too much! Work out the calculation first then round up the answer if necessary.

2. Is 60% of $80 the same as 80% of $60?

Yes,they are both $48.

3. Is GST always calculated at 12.5%?

Yes, in New Zealand GST is always 12.5% on all goods and all services. In some countries there is a different percentage for different types of goods and services.