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	$63.59	12.607%	$71.6068	$71.61	$71.60	$71.60
Purchase #2	$154.57	12.795%	$174.3472	$174.35	$174.35	$174.30
Purchase #3	$9.69	12.363%	$10.888	$10.89	$10.90	$10.90
Purchase #4	$25.52	9.382%	$27.9143	$27.91	$27.90	$27.90
Purchase #5	$13.58	6.248%	$14.4285	$14.43	$14.45	$14.40
Purchase #6	$152.82	13.308%	$173.1573	$173.16	$173.15	$173.20
Purchase #7	$126.93	11.687%	$141.7643	$141.76	$141.75	$141.80
7 purchase totals =	$546.70		$614.1064	$614.11	$614.10	$614.10