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	$155.41	10.771%	$172.1492	$172.15	$172.15	$172.10
Purchase #2	$124.88	5.567%	$131.8321	$131.83	$131.85	$131.80
Purchase #3	$68.38	4.102%	$71.1849	$71.18	$71.20	$71.20
Purchase #4	$140.78	13.512%	$159.8022	$159.80	$159.80	$159.80
Purchase #5	$53.84	13.470%	$61.0922	$61.09	$61.10	$61.10
Purchase #6	$47.74	12.657%	$53.7825	$53.78	$53.80	$53.80
Purchase #7	$206.87	7.493%	$222.3708	$222.37	$222.35	$222.40
7 purchase totals =	$797.90		$872.2139	$872.20	$872.25	$872.20