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	$220.36	4.583%	$230.4591	$230.46	$230.45	$230.50
Purchase #2	$153.97	4.292%	$160.5784	$160.58	$160.60	$160.60
Purchase #3	$160.52	5.248%	$168.9441	$168.94	$168.95	$168.90
Purchase #4	$39.67	10.536%	$43.8496	$43.85	$43.85	$43.80
Purchase #5	$186.73	5.388%	$196.791	$196.79	$196.80	$196.80
Purchase #6	$123.28	8.385%	$133.617	$133.62	$133.60	$133.60
Purchase #7	$193.28	10.117%	$212.8341	$212.83	$212.85	$212.80
7 purchase totals =	$1,077.81		$1,147.0733	$1,147.07	$1,147.10	$1,147.00