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	$142.82	9.161%	$155.9037	$155.90	$155.90	$155.90
Purchase #2	$238.87	4.235%	$248.9861	$248.99	$249.00	$249.00
Purchase #3	$242.80	7.291%	$260.5025	$260.50	$260.50	$260.50
Purchase #4	$119.85	6.749%	$127.9387	$127.94	$127.95	$127.90
Purchase #5	$173.80	4.193%	$181.0874	$181.09	$181.10	$181.10
Purchase #6	$101.29	10.248%	$111.6702	$111.67	$111.65	$111.70
Purchase #7	$57.28	7.385%	$61.5101	$61.51	$61.50	$61.50
7 purchase totals =	$1,076.71		$1,147.5987	$1,147.60	$1,147.60	$1,147.60