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	$62.65	8.284%	$67.8399	$67.84	$67.85	$67.80
Purchase #2	$18.88	7.165%	$20.2328	$20.23	$20.25	$20.20
Purchase #3	$190.63	3.161%	$196.6558	$196.66	$196.65	$196.70
Purchase #4	$158.28	9.182%	$172.8133	$172.81	$172.80	$172.80
Purchase #5	$88.66	11.874%	$99.1875	$99.19	$99.20	$99.20
Purchase #6	$61.29	12.290%	$68.8225	$68.82	$68.80	$68.80
Purchase #7	$68.76	3.554%	$71.2037	$71.20	$71.20	$71.20
7 purchase totals =	$649.15		$696.7555	$696.75	$696.75	$696.70