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	$63.84	10.595%	$70.6038	$70.60	$70.60	$70.60
Purchase #2	$102.25	9.432%	$111.8942	$111.89	$111.90	$111.90
Purchase #3	$19.50	8.602%	$21.1774	$21.18	$21.20	$21.20
Purchase #4	$56.56	12.204%	$63.4626	$63.46	$63.45	$63.50
Purchase #5	$68.52	10.482%	$75.7023	$75.70	$75.70	$75.70
Purchase #6	$231.33	10.287%	$255.1269	$255.13	$255.15	$255.10
Purchase #7	$137.51	10.320%	$151.701	$151.70	$151.70	$151.70
7 purchase totals =	$679.51		$749.6682	$749.66	$749.70	$749.70