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	$63.49	6.329%	$67.5083	$67.51	$67.50	$67.50
Purchase #2	$196.28	7.436%	$210.8754	$210.88	$210.90	$210.90
Purchase #3	$155.51	11.670%	$173.658	$173.66	$173.65	$173.70
Purchase #4	$223.52	13.244%	$253.123	$253.12	$253.10	$253.10
Purchase #5	$120.42	6.792%	$128.5989	$128.60	$128.60	$128.60
Purchase #6	$120.92	9.745%	$132.7037	$132.70	$132.70	$132.70
Purchase #7	$85.84	5.234%	$90.3329	$90.33	$90.35	$90.30
7 purchase totals =	$965.98		$1,056.8002	$1,056.80	$1,056.80	$1,056.80