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	$189.49	5.487%	$199.8873	$199.89	$199.90	$199.90
Purchase #2	$118.89	11.861%	$132.9915	$132.99	$133.00	$133.00
Purchase #3	$228.68	11.831%	$255.7351	$255.74	$255.75	$255.70
Purchase #4	$106.82	4.699%	$111.8395	$111.84	$111.85	$111.80
Purchase #5	$132.58	8.553%	$143.9196	$143.92	$143.90	$143.90
Purchase #6	$130.73	4.483%	$136.5906	$136.59	$136.60	$136.60
Purchase #7	$99.97	6.317%	$106.2851	$106.29	$106.30	$106.30
7 purchase totals =	$1,007.16		$1,087.2487	$1,087.26	$1,087.30	$1,087.20