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	$135.87	6.377%	$144.5344	$144.53	$144.55	$144.50
Purchase #2	$127.44	4.671%	$133.3927	$133.39	$133.40	$133.40
Purchase #3	$172.47	13.622%	$195.9639	$195.96	$195.95	$196.00
Purchase #4	$215.26	8.446%	$233.4409	$233.44	$233.45	$233.40
Purchase #5	$156.90	10.257%	$172.9932	$172.99	$173.00	$173.00
Purchase #6	$216.67	5.492%	$228.5695	$228.57	$228.55	$228.60
Purchase #7	$153.86	11.538%	$171.6124	$171.61	$171.60	$171.60
7 purchase totals =	$1,178.47		$1,280.5070	$1,280.49	$1,280.50	$1,280.50