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	$173.98	4.536%	$181.8717	$181.87	$181.85	$181.90
Purchase #2	$125.86	4.781%	$131.8774	$131.88	$131.90	$131.90
Purchase #3	$31.57	8.563%	$34.2733	$34.27	$34.25	$34.30
Purchase #4	$137.66	4.325%	$143.6138	$143.61	$143.60	$143.60
Purchase #5	$178.52	8.324%	$193.38	$193.38	$193.40	$193.40
Purchase #6	$60.68	5.472%	$64.0004	$64.00	$64.00	$64.00
Purchase #7	$62.77	6.457%	$66.8231	$66.82	$66.80	$66.80
7 purchase totals =	$771.04		$815.8397	$815.83	$815.80	$815.90