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	$224.57	8.617%	$243.9212	$243.92	$243.90	$243.90
Purchase #2	$204.95	8.300%	$221.9609	$221.96	$221.95	$222.00
Purchase #3	$205.60	4.795%	$215.4585	$215.46	$215.45	$215.50
Purchase #4	$99.95	12.288%	$112.2319	$112.23	$112.25	$112.20
Purchase #5	$206.50	11.351%	$229.9398	$229.94	$229.95	$229.90
Purchase #6	$160.52	7.594%	$172.7099	$172.71	$172.70	$172.70
Purchase #7	$232.78	9.503%	$254.9011	$254.90	$254.90	$254.90
7 purchase totals =	$1,334.87		$1,451.1233	$1,451.12	$1,451.10	$1,451.10