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	$57.82	10.538%	$63.9131	$63.91	$63.90	$63.90
Purchase #2	$232.83	9.571%	$255.1142	$255.11	$255.10	$255.10
Purchase #3	$229.39	11.139%	$254.9418	$254.94	$254.95	$254.90
Purchase #4	$22.45	7.610%	$24.1584	$24.16	$24.15	$24.20
Purchase #5	$74.67	13.164%	$84.4996	$84.50	$84.50	$84.50
Purchase #6	$153.32	8.580%	$166.4749	$166.47	$166.45	$166.50
Purchase #7	$210.83	10.573%	$233.1211	$233.12	$233.10	$233.10
7 purchase totals =	$981.31		$1,082.2231	$1,082.21	$1,082.15	$1,082.20