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	$195.88	13.685%	$222.6862	$222.69	$222.70	$222.70
Purchase #2	$49.60	9.199%	$54.1627	$54.16	$54.15	$54.20
Purchase #3	$146.69	6.726%	$156.5564	$156.56	$156.55	$156.60
Purchase #4	$7.28	9.870%	$7.9985	$8.00	$8.00	$8.00
Purchase #5	$126.31	10.151%	$139.1317	$139.13	$139.15	$139.10
Purchase #6	$244.72	5.369%	$257.859	$257.86	$257.85	$257.90
Purchase #7	$225.50	8.422%	$244.4916	$244.49	$244.50	$244.50
7 purchase totals =	$995.98		$1,082.8861	$1,082.89	$1,082.90	$1,083.00