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	$63.35	12.177%	$71.0641	$71.06	$71.05	$71.10
Purchase #2	$224.93	13.751%	$255.8601	$255.86	$255.85	$255.90
Purchase #3	$20.84	6.719%	$22.2402	$22.24	$22.25	$22.20
Purchase #4	$95.66	5.453%	$100.8763	$100.88	$100.90	$100.90
Purchase #5	$131.85	9.624%	$144.5392	$144.54	$144.55	$144.50
Purchase #6	$117.85	7.481%	$126.6664	$126.67	$126.65	$126.70
Purchase #7	$176.98	6.408%	$188.3209	$188.32	$188.30	$188.30
7 purchase totals =	$831.46		$909.5672	$909.57	$909.55	$909.60