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	$183.32	4.172%	$190.9681	$190.97	$190.95	$191.00
Purchase #2	$122.98	7.226%	$131.8665	$131.87	$131.85	$131.90
Purchase #3	$194.49	7.733%	$209.5299	$209.53	$209.55	$209.50
Purchase #4	$97.59	11.534%	$108.846	$108.85	$108.85	$108.80
Purchase #5	$105.71	4.553%	$110.523	$110.52	$110.50	$110.50
Purchase #6	$179.32	11.652%	$200.2144	$200.21	$200.20	$200.20
Purchase #7	$197.60	10.169%	$217.6939	$217.69	$217.70	$217.70
7 purchase totals =	$1,081.01		$1,169.6418	$1,169.64	$1,169.60	$1,169.60