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	$74.60	10.140%	$82.1644	$82.16	$82.15	$82.20
Purchase #2	$181.88	5.873%	$192.5618	$192.56	$192.55	$192.60
Purchase #3	$133.67	4.608%	$139.8295	$139.83	$139.85	$139.80
Purchase #4	$96.49	5.802%	$102.0883	$102.09	$102.10	$102.10
Purchase #5	$216.47	6.658%	$230.8826	$230.88	$230.90	$230.90
Purchase #6	$87.78	5.332%	$92.4604	$92.46	$92.45	$92.50
Purchase #7	$211.92	10.862%	$234.9388	$234.94	$234.95	$234.90
7 purchase totals =	$1,002.81		$1,074.9258	$1,074.92	$1,074.95	$1,075.00