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	$62.43	10.139%	$68.7598	$68.76	$68.75	$68.80
Purchase #2	$143.58	3.624%	$148.7833	$148.78	$148.80	$148.80
Purchase #3	$22.86	3.724%	$23.7113	$23.71	$23.70	$23.70
Purchase #4	$89.31	12.630%	$100.5899	$100.59	$100.60	$100.60
Purchase #5	$139.97	4.304%	$145.9943	$145.99	$146.00	$146.00
Purchase #6	$59.41	12.481%	$66.825	$66.83	$66.85	$66.80
Purchase #7	$88.82	13.178%	$100.5247	$100.52	$100.50	$100.50
7 purchase totals =	$606.38		$655.1883	$655.18	$655.20	$655.20