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	$233.79	12.241%	$262.4082	$262.41	$262.40	$262.40
Purchase #2	$84.55	7.208%	$90.6444	$90.64	$90.65	$90.60
Purchase #3	$43.71	13.253%	$49.5029	$49.50	$49.50	$49.50
Purchase #4	$34.75	7.690%	$37.4223	$37.42	$37.40	$37.40
Purchase #5	$210.48	3.849%	$218.5814	$218.58	$218.60	$218.60
Purchase #6	$241.38	6.378%	$256.7752	$256.78	$256.80	$256.80
Purchase #7	$43.51	11.256%	$48.4075	$48.41	$48.40	$48.40
7 purchase totals =	$892.17		$963.7419	$963.74	$963.75	$963.70