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	$52.63	13.334%	$59.6477	$59.65	$59.65	$59.60
Purchase #2	$40.83	7.126%	$43.7395	$43.74	$43.75	$43.70
Purchase #3	$108.65	12.641%	$122.3844	$122.38	$122.40	$122.40
Purchase #4	$243.25	9.409%	$266.1374	$266.14	$266.15	$266.10
Purchase #5	$133.76	5.487%	$141.0994	$141.10	$141.10	$141.10
Purchase #6	$116.67	5.773%	$123.4054	$123.41	$123.40	$123.40
Purchase #7	$172.38	3.367%	$178.184	$178.18	$178.20	$178.20
7 purchase totals =	$868.17		$934.5978	$934.60	$934.65	$934.50