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	$61.64	9.389%	$67.4274	$67.43	$67.45	$67.40
Purchase #2	$139.49	8.290%	$151.0537	$151.05	$151.05	$151.10
Purchase #3	$111.48	3.559%	$115.4476	$115.45	$115.45	$115.40
Purchase #4	$74.97	4.677%	$78.4763	$78.48	$78.50	$78.50
Purchase #5	$177.86	3.348%	$183.8148	$183.81	$183.80	$183.80
Purchase #6	$47.67	12.198%	$53.4848	$53.48	$53.50	$53.50
Purchase #7	$48.64	13.103%	$55.0133	$55.01	$55.00	$55.00
7 purchase totals =	$661.75		$704.7179	$704.71	$704.75	$704.70