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	$44.67	9.643%	$48.9775	$48.98	$49.00	$49.00
Purchase #2	$219.63	11.502%	$244.8918	$244.89	$244.90	$244.90
Purchase #3	$149.69	5.638%	$158.1295	$158.13	$158.15	$158.10
Purchase #4	$229.95	11.109%	$255.4951	$255.50	$255.50	$255.50
Purchase #5	$165.58	4.831%	$173.5792	$173.58	$173.60	$173.60
Purchase #6	$47.31	9.493%	$51.8011	$51.80	$51.80	$51.80
Purchase #7	$172.41	6.783%	$184.1046	$184.10	$184.10	$184.10
7 purchase totals =	$1,029.24		$1,116.9788	$1,116.98	$1,117.05	$1,117.00