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	$139.51	8.500%	$151.3684	$151.37	$151.35	$151.40
Purchase #2	$92.41	4.675%	$96.7302	$96.73	$96.75	$96.70
Purchase #3	$228.77	7.549%	$246.0398	$246.04	$246.05	$246.00
Purchase #4	$173.88	10.635%	$192.3721	$192.37	$192.35	$192.40
Purchase #5	$222.48	3.210%	$229.6216	$229.62	$229.60	$229.60
Purchase #6	$112.26	13.758%	$127.7047	$127.70	$127.70	$127.70
Purchase #7	$117.64	8.511%	$127.6523	$127.65	$127.65	$127.70
7 purchase totals =	$1,086.95		$1,171.4891	$1,171.48	$1,171.45	$1,171.50