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	$66.32	7.313%	$71.17	$71.17	$71.15	$71.20
Purchase #2	$11.38	12.145%	$12.7621	$12.76	$12.75	$12.80
Purchase #3	$5.80	11.655%	$6.476	$6.48	$6.50	$6.50
Purchase #4	$157.58	9.619%	$172.7376	$172.74	$172.75	$172.70
Purchase #5	$128.88	8.448%	$139.7678	$139.77	$139.75	$139.80
Purchase #6	$39.98	13.477%	$45.3681	$45.37	$45.35	$45.40
Purchase #7	$240.96	12.527%	$271.1451	$271.15	$271.15	$271.10
7 purchase totals =	$650.90		$719.4267	$719.44	$719.40	$719.50