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	$190.60	7.796%	$205.4592	$205.46	$205.45	$205.50
Purchase #2	$203.66	12.387%	$228.8874	$228.89	$228.90	$228.90
Purchase #3	$181.99	5.869%	$192.671	$192.67	$192.65	$192.70
Purchase #4	$61.87	3.708%	$64.1641	$64.16	$64.15	$64.20
Purchase #5	$111.54	13.164%	$126.2231	$126.22	$126.20	$126.20
Purchase #6	$223.85	4.611%	$234.1717	$234.17	$234.15	$234.20
Purchase #7	$90.37	10.744%	$100.0794	$100.08	$100.10	$100.10
7 purchase totals =	$1,063.88		$1,151.6559	$1,151.65	$1,151.60	$1,151.80