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	$70.60	11.103%	$78.4387	$78.44	$78.45	$78.40
Purchase #2	$7.67	12.465%	$8.6261	$8.63	$8.65	$8.60
Purchase #3	$18.76	13.172%	$21.2311	$21.23	$21.25	$21.20
Purchase #4	$152.57	13.672%	$173.4294	$173.43	$173.45	$173.40
Purchase #5	$146.47	8.350%	$158.7002	$158.70	$158.70	$158.70
Purchase #6	$134.82	11.787%	$150.7112	$150.71	$150.70	$150.70
Purchase #7	$198.68	5.532%	$209.671	$209.67	$209.65	$209.70
7 purchase totals =	$729.57		$800.8077	$800.81	$800.85	$800.70