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	$234.67	9.459%	$256.8674	$256.87	$256.85	$256.90
Purchase #2	$54.55	9.239%	$59.5899	$59.59	$59.60	$59.60
Purchase #3	$107.28	5.742%	$113.44	$113.44	$113.45	$113.40
Purchase #4	$106.53	4.577%	$111.4059	$111.41	$111.40	$111.40
Purchase #5	$124.46	13.439%	$141.1862	$141.19	$141.20	$141.20
Purchase #6	$132.84	9.484%	$145.4385	$145.44	$145.45	$145.40
Purchase #7	$108.46	7.178%	$116.2453	$116.25	$116.25	$116.20
7 purchase totals =	$868.79		$944.1732	$944.19	$944.20	$944.10