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	$208.86	6.724%	$222.9037	$222.90	$222.90	$222.90
Purchase #2	$158.74	9.469%	$173.7711	$173.77	$173.75	$173.80
Purchase #3	$138.74	3.328%	$143.3573	$143.36	$143.35	$143.40
Purchase #4	$41.81	9.712%	$45.8706	$45.87	$45.85	$45.90
Purchase #5	$195.75	11.494%	$218.2495	$218.25	$218.25	$218.20
Purchase #6	$172.70	7.250%	$185.2208	$185.22	$185.20	$185.20
Purchase #7	$12.47	13.549%	$14.1596	$14.16	$14.15	$14.20
7 purchase totals =	$929.07		$1,003.5326	$1,003.53	$1,003.45	$1,003.60