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	$133.66	13.166%	$151.2577	$151.26	$151.25	$151.30
Purchase #2	$106.48	11.128%	$118.3291	$118.33	$118.35	$118.30
Purchase #3	$35.29	10.119%	$38.861	$38.86	$38.85	$38.90
Purchase #4	$107.46	3.364%	$111.075	$111.08	$111.10	$111.10
Purchase #5	$247.97	3.283%	$256.1109	$256.11	$256.10	$256.10
Purchase #6	$143.47	4.712%	$150.2303	$150.23	$150.25	$150.20
Purchase #7	$83.64	8.314%	$90.5938	$90.59	$90.60	$90.60
7 purchase totals =	$857.97		$916.4578	$916.46	$916.50	$916.50