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	$127.43	3.688%	$132.1296	$132.13	$132.15	$132.10
Purchase #2	$154.59	4.387%	$161.3719	$161.37	$161.35	$161.40
Purchase #3	$52.31	13.367%	$59.3023	$59.30	$59.30	$59.30
Purchase #4	$105.45	7.742%	$113.6139	$113.61	$113.60	$113.60
Purchase #5	$139.43	4.874%	$146.2258	$146.23	$146.25	$146.20
Purchase #6	$60.83	5.361%	$64.0911	$64.09	$64.10	$64.10
Purchase #7	$201.27	12.205%	$225.835	$225.84	$225.85	$225.80
7 purchase totals =	$841.31		$902.5696	$902.57	$902.60	$902.50