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	$164.51	12.874%	$185.689	$185.69	$185.70	$185.70
Purchase #2	$105.69	3.683%	$109.5826	$109.58	$109.60	$109.60
Purchase #3	$194.64	8.147%	$210.4973	$210.50	$210.50	$210.50
Purchase #4	$247.92	4.359%	$258.7268	$258.73	$258.75	$258.70
Purchase #5	$138.83	13.532%	$157.6165	$157.62	$157.60	$157.60
Purchase #6	$129.45	10.798%	$143.428	$143.43	$143.45	$143.40
Purchase #7	$217.78	11.492%	$242.8073	$242.81	$242.80	$242.80
7 purchase totals =	$1,198.82		$1,308.3475	$1,308.36	$1,308.40	$1,308.30