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	$120.27	5.480%	$126.8608	$126.86	$126.85	$126.90
Purchase #2	$133.83	13.480%	$151.8703	$151.87	$151.85	$151.90
Purchase #3	$99.52	4.392%	$103.8909	$103.89	$103.90	$103.90
Purchase #4	$88.99	12.680%	$100.2739	$100.27	$100.25	$100.30
Purchase #5	$230.40	11.480%	$256.8499	$256.85	$256.85	$256.80
Purchase #6	$94.68	13.164%	$107.1437	$107.14	$107.15	$107.10
Purchase #7	$211.83	10.128%	$233.2841	$233.28	$233.30	$233.30
7 purchase totals =	$979.52		$1,080.1736	$1,080.16	$1,080.15	$1,080.20