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	$63.27	6.414%	$67.3281	$67.33	$67.35	$67.30
Purchase #2	$105.55	5.716%	$111.5832	$111.58	$111.60	$111.60
Purchase #3	$127.99	3.581%	$132.5733	$132.57	$132.55	$132.60
Purchase #4	$10.48	13.392%	$11.8835	$11.88	$11.90	$11.90
Purchase #5	$15.67	11.660%	$17.4971	$17.50	$17.50	$17.50
Purchase #6	$163.88	12.382%	$184.1716	$184.17	$184.15	$184.20
Purchase #7	$196.80	13.423%	$223.2165	$223.22	$223.20	$223.20
7 purchase totals =	$683.64		$748.2533	$748.25	$748.25	$748.30