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	$164.89	4.107%	$171.662	$171.66	$171.65	$171.70
Purchase #2	$8.93	6.842%	$9.541	$9.54	$9.55	$9.50
Purchase #3	$248.78	3.123%	$256.5494	$256.55	$256.55	$256.50
Purchase #4	$116.43	10.171%	$128.2721	$128.27	$128.25	$128.30
Purchase #5	$48.75	12.553%	$54.8696	$54.87	$54.85	$54.90
Purchase #6	$23.83	5.523%	$25.1461	$25.15	$25.15	$25.10
Purchase #7	$126.59	8.613%	$137.4932	$137.49	$137.50	$137.50
7 purchase totals =	$738.20		$783.5334	$783.53	$783.50	$783.50