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	$57.45	9.469%	$62.8899	$62.89	$62.90	$62.90
Purchase #2	$28.82	6.737%	$30.7616	$30.76	$30.75	$30.80
Purchase #3	$159.50	8.203%	$172.5838	$172.58	$172.60	$172.60
Purchase #4	$80.41	13.138%	$90.9743	$90.97	$90.95	$91.00
Purchase #5	$48.97	7.120%	$52.4567	$52.46	$52.45	$52.50
Purchase #6	$12.76	8.219%	$13.8087	$13.81	$13.80	$13.80
Purchase #7	$249.41	12.387%	$280.3044	$280.30	$280.30	$280.30
7 purchase totals =	$637.32		$703.7794	$703.77	$703.75	$703.90