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	$250.68	12.777%	$282.7094	$282.71	$282.70	$282.70
Purchase #2	$56.51	11.189%	$62.8329	$62.83	$62.85	$62.80
Purchase #3	$166.54	3.729%	$172.7503	$172.75	$172.75	$172.80
Purchase #4	$50.57	3.774%	$52.4785	$52.48	$52.50	$52.50
Purchase #5	$32.32	5.683%	$34.1567	$34.16	$34.15	$34.20
Purchase #6	$192.89	9.144%	$210.5279	$210.53	$210.55	$210.50
Purchase #7	$186.58	12.527%	$209.9529	$209.95	$209.95	$210.00
7 purchase totals =	$936.09		$1,025.4086	$1,025.41	$1,025.45	$1,025.50