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	$239.93	11.198%	$266.7974	$266.80	$266.80	$266.80
Purchase #2	$85.38	5.619%	$90.1775	$90.18	$90.20	$90.20
Purchase #3	$200.27	6.608%	$213.5038	$213.50	$213.50	$213.50
Purchase #4	$242.45	13.799%	$275.9057	$275.91	$275.90	$275.90
Purchase #5	$11.58	11.238%	$12.8814	$12.88	$12.90	$12.90
Purchase #6	$206.62	7.522%	$222.162	$222.16	$222.15	$222.20
Purchase #7	$63.79	13.429%	$72.3564	$72.36	$72.35	$72.40
7 purchase totals =	$1,050.02		$1,153.7842	$1,153.79	$1,153.80	$1,153.90