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	$175.98	11.605%	$196.4025	$196.40	$196.40	$196.40
Purchase #2	$26.80	13.710%	$30.4743	$30.47	$30.45	$30.50
Purchase #3	$129.65	12.473%	$145.8212	$145.82	$145.80	$145.80
Purchase #4	$209.52	6.335%	$222.7931	$222.79	$222.80	$222.80
Purchase #5	$29.40	3.769%	$30.5081	$30.51	$30.50	$30.50
Purchase #6	$54.69	10.572%	$60.4718	$60.47	$60.45	$60.50
Purchase #7	$116.75	13.802%	$132.8638	$132.86	$132.85	$132.90
7 purchase totals =	$742.79		$819.3348	$819.32	$819.25	$819.40