Aside from the cents bit, it's like that in Australia too. If something (retail) says $30 then it's $30. If it says $30.95 then it's $30.95. It's very simple. When you're selling wholesale it's different because it's a sales tax, and that's paid by the consumer, not the retail business.
Sales tax is charged only once for a retail good, not for the sales of wholesale goods that led to the retail sale. Otherwise the store that sold you a thing would itself have also had to pay 10% on that thing, as would the factory that bought the raw materials to make the thing, etc.
