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	$198.87	3.591%	$206.0114	$206.01	$206.00	$206.00
Purchase #2	$122.82	3.315%	$126.8915	$126.89	$126.90	$126.90
Purchase #3	$125.66	11.370%	$139.9475	$139.95	$139.95	$139.90
Purchase #4	$190.66	3.222%	$196.8031	$196.80	$196.80	$196.80
Purchase #5	$130.72	8.586%	$141.9436	$141.94	$141.95	$141.90
Purchase #6	$241.89	11.477%	$269.6517	$269.65	$269.65	$269.70
Purchase #7	$38.52	5.826%	$40.7642	$40.76	$40.75	$40.80
7 purchase totals =	$1,049.14		$1,122.0130	$1,122.00	$1,122.00	$1,122.00