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	$97.66	11.437%	$108.8294	$108.83	$108.85	$108.80
Purchase #2	$146.69	5.250%	$154.3912	$154.39	$154.40	$154.40
Purchase #3	$128.31	6.229%	$136.3024	$136.30	$136.30	$136.30
Purchase #4	$220.54	6.536%	$234.9545	$234.95	$234.95	$235.00
Purchase #5	$62.27	8.826%	$67.766	$67.77	$67.75	$67.80
Purchase #6	$36.47	9.757%	$40.0284	$40.03	$40.05	$40.00
Purchase #7	$192.45	4.245%	$200.6195	$200.62	$200.60	$200.60
7 purchase totals =	$884.39		$942.8914	$942.89	$942.90	$942.90