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	$103.34	6.235%	$109.7832	$109.78	$109.80	$109.80
Purchase #2	$46.51	4.196%	$48.4616	$48.46	$48.45	$48.50
Purchase #3	$174.37	5.458%	$183.8871	$183.89	$183.90	$183.90
Purchase #4	$159.47	6.563%	$169.936	$169.94	$169.95	$169.90
Purchase #5	$14.90	4.536%	$15.5759	$15.58	$15.60	$15.60
Purchase #6	$53.90	5.525%	$56.878	$56.88	$56.90	$56.90
Purchase #7	$172.42	10.754%	$190.962	$190.96	$190.95	$191.00
7 purchase totals =	$724.91		$775.4838	$775.49	$775.55	$775.60