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	$218.75	3.186%	$225.7194	$225.72	$225.70	$225.70
Purchase #2	$121.35	6.619%	$129.3822	$129.38	$129.40	$129.40
Purchase #3	$73.37	6.510%	$78.1464	$78.15	$78.15	$78.10
Purchase #4	$203.25	13.607%	$230.9062	$230.91	$230.90	$230.90
Purchase #5	$114.31	11.407%	$127.3493	$127.35	$127.35	$127.30
Purchase #6	$154.81	11.731%	$172.9708	$172.97	$172.95	$173.00
Purchase #7	$210.69	3.707%	$218.5003	$218.50	$218.50	$218.50
7 purchase totals =	$1,096.53		$1,182.9746	$1,182.98	$1,182.95	$1,182.90