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	$77.29	10.515%	$85.417	$85.42	$85.40	$85.40
Purchase #2	$79.80	4.844%	$83.6655	$83.67	$83.65	$83.70
Purchase #3	$200.37	11.198%	$222.8074	$222.81	$222.80	$222.80
Purchase #4	$100.82	10.359%	$111.2639	$111.26	$111.25	$111.30
Purchase #5	$218.76	6.593%	$233.1828	$233.18	$233.20	$233.20
Purchase #6	$94.66	8.595%	$102.796	$102.80	$102.80	$102.80
Purchase #7	$56.73	3.575%	$58.7581	$58.76	$58.75	$58.80
7 purchase totals =	$828.43		$897.8907	$897.90	$897.85	$898.00