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	$205.29	11.481%	$228.8593	$228.86	$228.85	$228.90
Purchase #2	$181.37	13.347%	$205.5775	$205.58	$205.60	$205.60
Purchase #3	$149.43	3.637%	$154.8648	$154.86	$154.85	$154.90
Purchase #4	$106.80	4.738%	$111.8602	$111.86	$111.85	$111.90
Purchase #5	$7.53	8.219%	$8.1489	$8.15	$8.15	$8.10
Purchase #6	$133.70	4.865%	$140.2045	$140.20	$140.20	$140.20
Purchase #7	$44.64	13.107%	$50.491	$50.49	$50.50	$50.50
7 purchase totals =	$828.76		$900.0062	$900.00	$900.00	$900.10