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	$168.74	13.717%	$191.8861	$191.89	$191.90	$191.90
Purchase #2	$138.27	3.748%	$143.4524	$143.45	$143.45	$143.50
Purchase #3	$82.87	4.776%	$86.8279	$86.83	$86.85	$86.80
Purchase #4	$185.89	10.580%	$205.5572	$205.56	$205.55	$205.60
Purchase #5	$142.99	12.571%	$160.9653	$160.97	$160.95	$161.00
Purchase #6	$87.43	5.393%	$92.1451	$92.15	$92.15	$92.10
Purchase #7	$103.78	8.559%	$112.6625	$112.66	$112.65	$112.70
7 purchase totals =	$909.97		$993.4965	$993.51	$993.50	$993.60