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	$14.25	5.377%	$15.0162	$15.02	$15.00	$15.00
Purchase #2	$143.89	9.844%	$158.0545	$158.05	$158.05	$158.10
Purchase #3	$131.58	11.329%	$146.4867	$146.49	$146.50	$146.50
Purchase #4	$161.35	7.424%	$173.3286	$173.33	$173.35	$173.30
Purchase #5	$49.31	3.667%	$51.1182	$51.12	$51.10	$51.10
Purchase #6	$178.28	11.755%	$199.2368	$199.24	$199.25	$199.20
Purchase #7	$154.71	11.514%	$172.5233	$172.52	$172.50	$172.50
7 purchase totals =	$833.37		$915.7643	$915.77	$915.75	$915.70