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	$65.68	3.320%	$67.8606	$67.86	$67.85	$67.90
Purchase #2	$249.78	3.653%	$258.9045	$258.90	$258.90	$258.90
Purchase #3	$173.37	4.169%	$180.5978	$180.60	$180.60	$180.60
Purchase #4	$84.57	7.234%	$90.6878	$90.69	$90.70	$90.70
Purchase #5	$40.88	13.558%	$46.4225	$46.42	$46.40	$46.40
Purchase #6	$10.95	5.563%	$11.5591	$11.56	$11.55	$11.60
Purchase #7	$8.54	11.671%	$9.5367	$9.54	$9.55	$9.50
7 purchase totals =	$633.77		$665.5690	$665.57	$665.55	$665.60