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	$60.85	9.196%	$66.4458	$66.45	$66.45	$66.40
Purchase #2	$114.31	12.847%	$128.9954	$129.00	$129.00	$129.00
Purchase #3	$62.73	6.419%	$66.7566	$66.76	$66.75	$66.80
Purchase #4	$194.92	12.435%	$219.1583	$219.16	$219.15	$219.20
Purchase #5	$128.67	3.612%	$133.3176	$133.32	$133.30	$133.30
Purchase #6	$117.47	8.504%	$127.4596	$127.46	$127.45	$127.50
Purchase #7	$101.94	4.366%	$106.3907	$106.39	$106.40	$106.40
7 purchase totals =	$780.89		$848.5240	$848.54	$848.50	$848.60