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	$139.69	10.365%	$154.1689	$154.17	$154.15	$154.20
Purchase #2	$99.69	11.578%	$111.2321	$111.23	$111.25	$111.20
Purchase #3	$215.56	3.414%	$222.9192	$222.92	$222.90	$222.90
Purchase #4	$91.70	7.683%	$98.7453	$98.75	$98.75	$98.70
Purchase #5	$247.34	12.582%	$278.4603	$278.46	$278.45	$278.50
Purchase #6	$129.89	10.627%	$143.6934	$143.69	$143.70	$143.70
Purchase #7	$13.90	7.453%	$14.936	$14.94	$14.95	$14.90
7 purchase totals =	$937.77		$1,024.1552	$1,024.16	$1,024.15	$1,024.10