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	$93.32	10.433%	$103.0561	$103.06	$103.05	$103.10
Purchase #2	$198.95	11.438%	$221.7059	$221.71	$221.70	$221.70
Purchase #3	$79.83	13.517%	$90.6206	$90.62	$90.60	$90.60
Purchase #4	$203.35	4.262%	$212.0168	$212.02	$212.00	$212.00
Purchase #5	$211.78	6.456%	$225.4525	$225.45	$225.45	$225.50
Purchase #6	$53.32	6.137%	$56.5922	$56.59	$56.60	$56.60
Purchase #7	$231.79	10.833%	$256.8998	$256.90	$256.90	$256.90
7 purchase totals =	$1,072.34		$1,166.3439	$1,166.35	$1,166.30	$1,166.40