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	$137.38	10.391%	$151.6552	$151.66	$151.65	$151.70
Purchase #2	$83.98	5.244%	$88.3839	$88.38	$88.40	$88.40
Purchase #3	$153.53	13.826%	$174.7571	$174.76	$174.75	$174.80
Purchase #4	$125.80	4.823%	$131.8673	$131.87	$131.85	$131.90
Purchase #5	$46.98	7.376%	$50.4452	$50.45	$50.45	$50.40
Purchase #6	$196.90	11.236%	$219.0237	$219.02	$219.00	$219.00
Purchase #7	$87.50	8.873%	$95.2639	$95.26	$95.25	$95.30
7 purchase totals =	$832.07		$911.3963	$911.40	$911.35	$911.50