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	$177.28	12.866%	$200.0888	$200.09	$200.10	$200.10
Purchase #2	$132.66	11.650%	$148.1149	$148.11	$148.10	$148.10
Purchase #3	$206.67	4.250%	$215.4535	$215.45	$215.45	$215.50
Purchase #4	$161.94	8.532%	$175.7567	$175.76	$175.75	$175.80
Purchase #5	$181.92	6.580%	$193.8903	$193.89	$193.90	$193.90
Purchase #6	$120.60	4.484%	$126.0077	$126.01	$126.00	$126.00
Purchase #7	$38.31	5.454%	$40.3994	$40.40	$40.40	$40.40
7 purchase totals =	$1,019.38		$1,099.7113	$1,099.71	$1,099.70	$1,099.80