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	$128.26	11.828%	$143.4306	$143.43	$143.45	$143.40
Purchase #2	$173.55	5.167%	$182.5173	$182.52	$182.50	$182.50
Purchase #3	$113.71	3.655%	$117.8661	$117.87	$117.85	$117.90
Purchase #4	$233.43	9.407%	$255.3888	$255.39	$255.40	$255.40
Purchase #5	$68.73	4.767%	$72.0064	$72.01	$72.00	$72.00
Purchase #6	$105.52	5.387%	$111.2044	$111.20	$111.20	$111.20
Purchase #7	$134.83	10.618%	$149.1462	$149.15	$149.15	$149.10
7 purchase totals =	$958.03		$1,031.5598	$1,031.57	$1,031.55	$1,031.50