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	$65.56	10.502%	$72.4451	$72.45	$72.45	$72.40
Purchase #2	$246.37	3.730%	$255.5596	$255.56	$255.55	$255.60
Purchase #3	$155.48	8.484%	$168.6709	$168.67	$168.65	$168.70
Purchase #4	$58.75	12.732%	$66.2301	$66.23	$66.25	$66.20
Purchase #5	$242.70	10.256%	$267.5913	$267.59	$267.60	$267.60
Purchase #6	$113.26	11.735%	$126.5511	$126.55	$126.55	$126.60
Purchase #7	$108.83	9.285%	$118.9349	$118.93	$118.95	$118.90
7 purchase totals =	$990.95		$1,075.9830	$1,075.98	$1,076.00	$1,076.00