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	$77.62	10.399%	$85.6917	$85.69	$85.70	$85.70
Purchase #2	$152.98	9.247%	$167.1261	$167.13	$167.15	$167.10
Purchase #3	$199.90	6.422%	$212.7376	$212.74	$212.75	$212.70
Purchase #4	$52.66	11.282%	$58.6011	$58.60	$58.60	$58.60
Purchase #5	$173.78	10.304%	$191.6863	$191.69	$191.70	$191.70
Purchase #6	$52.86	12.452%	$59.4421	$59.44	$59.45	$59.40
Purchase #7	$184.80	10.159%	$203.5738	$203.57	$203.55	$203.60
7 purchase totals =	$894.60		$978.8587	$978.86	$978.90	$978.80