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	$56.72	10.805%	$62.8486	$62.85	$62.85	$62.80
Purchase #2	$112.95	5.173%	$118.7929	$118.79	$118.80	$118.80
Purchase #3	$132.27	11.869%	$147.9691	$147.97	$147.95	$148.00
Purchase #4	$99.56	12.651%	$112.1553	$112.16	$112.15	$112.20
Purchase #5	$210.86	9.319%	$230.51	$230.51	$230.50	$230.50
Purchase #6	$149.89	5.733%	$158.4832	$158.48	$158.50	$158.50
Purchase #7	$56.98	9.146%	$62.1914	$62.19	$62.20	$62.20
7 purchase totals =	$819.23		$892.9505	$892.95	$892.95	$893.00