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	$60.48	8.632%	$65.7006	$65.70	$65.70	$65.70
Purchase #2	$179.68	6.448%	$191.2658	$191.27	$191.25	$191.30
Purchase #3	$129.45	6.350%	$137.6701	$137.67	$137.65	$137.70
Purchase #4	$58.50	4.531%	$61.1506	$61.15	$61.15	$61.20
Purchase #5	$41.92	10.109%	$46.1577	$46.16	$46.15	$46.20
Purchase #6	$231.92	10.771%	$256.9001	$256.90	$256.90	$256.90
Purchase #7	$87.82	3.308%	$90.7251	$90.73	$90.75	$90.70
7 purchase totals =	$789.77		$849.5700	$849.58	$849.55	$849.70