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	$207.77	4.508%	$217.1363	$217.14	$217.15	$217.10
Purchase #2	$9.81	9.790%	$10.7704	$10.77	$10.75	$10.80
Purchase #3	$45.40	6.849%	$48.5094	$48.51	$48.50	$48.50
Purchase #4	$103.40	9.677%	$113.406	$113.41	$113.40	$113.40
Purchase #5	$119.33	8.714%	$129.7284	$129.73	$129.75	$129.70
Purchase #6	$80.42	11.563%	$89.719	$89.72	$89.70	$89.70
Purchase #7	$42.56	7.688%	$45.832	$45.83	$45.85	$45.80
7 purchase totals =	$608.69		$655.1015	$655.11	$655.10	$655.00