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	$136.31	3.486%	$141.0618	$141.06	$141.05	$141.10
Purchase #2	$148.58	10.801%	$164.6281	$164.63	$164.65	$164.60
Purchase #3	$231.42	11.636%	$258.348	$258.35	$258.35	$258.30
Purchase #4	$159.78	11.797%	$178.6292	$178.63	$178.65	$178.60
Purchase #5	$187.60	3.103%	$193.4212	$193.42	$193.40	$193.40
Purchase #6	$21.39	9.660%	$23.4563	$23.46	$23.45	$23.50
Purchase #7	$99.61	12.108%	$111.6708	$111.67	$111.65	$111.70
7 purchase totals =	$984.69		$1,071.2154	$1,071.22	$1,071.20	$1,071.20