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	$196.97	12.845%	$222.2708	$222.27	$222.25	$222.30
Purchase #2	$182.90	4.326%	$190.8123	$190.81	$190.80	$190.80
Purchase #3	$144.82	12.847%	$163.425	$163.43	$163.45	$163.40
Purchase #4	$126.94	7.591%	$136.576	$136.58	$136.60	$136.60
Purchase #5	$83.85	9.857%	$92.1151	$92.12	$92.10	$92.10
Purchase #6	$78.27	9.492%	$85.6994	$85.70	$85.70	$85.70
Purchase #7	$168.78	13.798%	$192.0683	$192.07	$192.05	$192.10
7 purchase totals =	$982.53		$1,082.9669	$1,082.98	$1,082.95	$1,083.00