Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$63.81	13.476%	$72.409	$72.41	$72.40	$72.40
Purchase #2	$42.78	3.577%	$44.3102	$44.31	$44.30	$44.30
Purchase #3	$91.42	10.520%	$101.0374	$101.04	$101.05	$101.00
Purchase #4	$88.31	11.552%	$98.5116	$98.51	$98.50	$98.50
Purchase #5	$48.45	8.265%	$52.4544	$52.45	$52.45	$52.50
Purchase #6	$32.56	5.820%	$34.455	$34.46	$34.45	$34.50
Purchase #7	$226.38	11.338%	$252.047	$252.05	$252.05	$252.00
7 purchase totals =	$593.71		$655.2246	$655.23	$655.20	$655.20