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	$11.46	13.806%	$13.0422	$13.04	$13.05	$13.00
Purchase #2	$105.50	12.251%	$118.4248	$118.42	$118.40	$118.40
Purchase #3	$195.62	11.217%	$217.5627	$217.56	$217.55	$217.60
Purchase #4	$176.77	12.756%	$199.3188	$199.32	$199.30	$199.30
Purchase #5	$197.72	12.643%	$222.7177	$222.72	$222.70	$222.70
Purchase #6	$136.37	9.215%	$148.9365	$148.94	$148.95	$148.90
Purchase #7	$134.96	6.682%	$143.978	$143.98	$144.00	$144.00
7 purchase totals =	$958.40		$1,063.9807	$1,063.98	$1,063.95	$1,063.90