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	$246.66	10.149%	$271.6935	$271.69	$271.70	$271.70
Purchase #2	$107.38	11.246%	$119.456	$119.46	$119.45	$119.50
Purchase #3	$157.91	10.755%	$174.8932	$174.89	$174.90	$174.90
Purchase #4	$81.94	10.708%	$90.7141	$90.71	$90.70	$90.70
Purchase #5	$221.38	3.389%	$228.8826	$228.88	$228.90	$228.90
Purchase #6	$184.76	10.561%	$204.2725	$204.27	$204.25	$204.30
Purchase #7	$6.43	4.394%	$6.7125	$6.71	$6.70	$6.70
7 purchase totals =	$1,006.46		$1,096.6244	$1,096.61	$1,096.60	$1,096.70