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	$229.80	11.745%	$256.79	$256.79	$256.80	$256.80
Purchase #2	$39.36	8.500%	$42.7056	$42.71	$42.70	$42.70
Purchase #3	$242.51	5.641%	$256.19	$256.19	$256.20	$256.20
Purchase #4	$19.62	9.849%	$21.5524	$21.55	$21.55	$21.60
Purchase #5	$68.85	7.590%	$74.0757	$74.08	$74.10	$74.10
Purchase #6	$137.59	10.762%	$152.3974	$152.40	$152.40	$152.40
Purchase #7	$233.94	9.130%	$255.2987	$255.30	$255.30	$255.30
7 purchase totals =	$971.67		$1,059.0098	$1,059.02	$1,059.05	$1,059.10