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	$67.85	6.796%	$72.4611	$72.46	$72.45	$72.50
Purchase #2	$57.64	12.868%	$65.0571	$65.06	$65.05	$65.10
Purchase #3	$126.57	4.773%	$132.6112	$132.61	$132.60	$132.60
Purchase #4	$28.45	8.113%	$30.7581	$30.76	$30.75	$30.80
Purchase #5	$48.31	12.162%	$54.1855	$54.19	$54.20	$54.20
Purchase #6	$50.31	10.694%	$55.6902	$55.69	$55.70	$55.70
Purchase #7	$137.47	12.735%	$154.9768	$154.98	$155.00	$155.00
7 purchase totals =	$516.60		$565.7400	$565.75	$565.75	$565.90