You need to understand that there is a difference between Zero Rated and Exempt.
Zero Rated are goods and services that basically are taxable, but the legislator decided to rate it at a "0" rate (for now). Whenever the government feels the need to collect more money, they can rate the zero rated goods or services at the rate they want.
Exempt means that goods or services are not taxable.
A grant is an exempt item.
The tip on the restaurant bill is an exempt item.
Bank fees are exempt items.
Cash payment on honorariums, is not exempt nor zero rated. Honorariums basically are taxable, and the entity or person who collects the honorariums must issue an invoice. It will include HST if the entity is HST registered. The payment method is irrelevant of the tax. If you pay cash, by cheque or credit card is not related to the tax.
Hope this helps.