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	$124.65	13.707%	$141.7358	$141.74	$141.75	$141.70
Purchase #2	$137.37	11.793%	$153.57	$153.57	$153.55	$153.60
Purchase #3	$111.30	8.257%	$120.49	$120.49	$120.50	$120.50
Purchase #4	$16.84	9.867%	$18.5016	$18.50	$18.50	$18.50
Purchase #5	$231.85	3.519%	$240.0088	$240.01	$240.00	$240.00
Purchase #6	$146.85	4.282%	$153.1381	$153.14	$153.15	$153.10
Purchase #7	$228.92	11.395%	$255.0054	$255.01	$255.00	$255.00
7 purchase totals =	$997.78		$1,082.4497	$1,082.46	$1,082.45	$1,082.40