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	$30.43	9.703%	$33.3826	$33.38	$33.40	$33.40
Purchase #2	$214.83	12.626%	$241.9544	$241.95	$241.95	$242.00
Purchase #3	$241.87	6.248%	$256.982	$256.98	$257.00	$257.00
Purchase #4	$98.46	13.699%	$111.948	$111.95	$111.95	$111.90
Purchase #5	$13.99	8.476%	$15.1758	$15.18	$15.20	$15.20
Purchase #6	$149.35	7.750%	$160.9246	$160.92	$160.90	$160.90
Purchase #7	$233.69	9.169%	$255.117	$255.12	$255.10	$255.10
7 purchase totals =	$982.62		$1,075.4844	$1,075.48	$1,075.50	$1,075.50