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	$29.90	8.268%	$32.3721	$32.37	$32.35	$32.40
Purchase #2	$190.32	3.205%	$196.4198	$196.42	$196.40	$196.40
Purchase #3	$210.49	3.225%	$217.2783	$217.28	$217.30	$217.30
Purchase #4	$235.93	13.397%	$267.5375	$267.54	$267.55	$267.50
Purchase #5	$241.63	10.160%	$266.1796	$266.18	$266.20	$266.20
Purchase #6	$107.72	13.807%	$122.5929	$122.59	$122.60	$122.60
Purchase #7	$111.41	8.699%	$121.1016	$121.10	$121.10	$121.10
7 purchase totals =	$1,127.40		$1,223.4818	$1,223.48	$1,223.50	$1,223.50