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	$170.61	11.691%	$190.556	$190.56	$190.55	$190.60
Purchase #2	$150.98	9.699%	$165.6236	$165.62	$165.60	$165.60
Purchase #3	$211.49	12.555%	$238.0426	$238.04	$238.05	$238.00
Purchase #4	$200.52	11.285%	$223.1487	$223.15	$223.15	$223.10
Purchase #5	$100.28	11.494%	$111.8062	$111.81	$111.80	$111.80
Purchase #6	$43.89	9.373%	$48.0038	$48.00	$48.00	$48.00
Purchase #7	$218.97	4.786%	$229.4499	$229.45	$229.45	$229.40
7 purchase totals =	$1,096.74		$1,206.6308	$1,206.63	$1,206.60	$1,206.50