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	$112.91	3.465%	$116.8223	$116.82	$116.80	$116.80
Purchase #2	$72.75	10.337%	$80.2702	$80.27	$80.25	$80.30
Purchase #3	$222.82	4.269%	$232.3322	$232.33	$232.35	$232.30
Purchase #4	$68.78	5.312%	$72.4336	$72.43	$72.45	$72.40
Purchase #5	$42.57	11.622%	$47.5175	$47.52	$47.50	$47.50
Purchase #6	$16.52	5.344%	$17.4028	$17.40	$17.40	$17.40
Purchase #7	$208.48	12.551%	$234.6463	$234.65	$234.65	$234.60
7 purchase totals =	$744.83		$801.4249	$801.42	$801.40	$801.30