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	$27.90	4.516%	$29.16	$29.16	$29.15	$29.20
Purchase #2	$203.98	12.278%	$229.0247	$229.02	$229.00	$229.00
Purchase #3	$50.67	8.356%	$54.904	$54.90	$54.90	$54.90
Purchase #4	$156.82	10.612%	$173.4617	$173.46	$173.45	$173.50
Purchase #5	$106.89	4.570%	$111.7749	$111.77	$111.75	$111.80
Purchase #6	$217.52	5.542%	$229.575	$229.58	$229.60	$229.60
Purchase #7	$169.25	8.846%	$184.2219	$184.22	$184.20	$184.20
7 purchase totals =	$933.03		$1,012.1222	$1,012.11	$1,012.05	$1,012.20