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	$228.63	12.247%	$256.6303	$256.63	$256.65	$256.60
Purchase #2	$202.35	9.574%	$221.723	$221.72	$221.70	$221.70
Purchase #3	$92.85	11.558%	$103.5816	$103.58	$103.60	$103.60
Purchase #4	$48.91	6.677%	$52.1757	$52.18	$52.20	$52.20
Purchase #5	$163.94	5.469%	$172.9059	$172.91	$172.90	$172.90
Purchase #6	$121.55	7.261%	$130.3757	$130.38	$130.40	$130.40
Purchase #7	$88.94	11.309%	$98.9982	$99.00	$99.00	$99.00
7 purchase totals =	$947.17		$1,036.3904	$1,036.40	$1,036.45	$1,036.40