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	$145.68	6.315%	$154.8797	$154.88	$154.90	$154.90
Purchase #2	$223.40	10.246%	$246.2896	$246.29	$246.30	$246.30
Purchase #3	$148.66	3.837%	$154.3641	$154.36	$154.35	$154.40
Purchase #4	$169.57	11.741%	$189.4792	$189.48	$189.50	$189.50
Purchase #5	$118.78	4.117%	$123.6702	$123.67	$123.65	$123.70
Purchase #6	$82.84	13.262%	$93.8262	$93.83	$93.85	$93.80
Purchase #7	$111.38	7.381%	$119.601	$119.60	$119.60	$119.60
7 purchase totals =	$1,000.31		$1,082.1100	$1,082.11	$1,082.15	$1,082.20