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	$12.77	4.636%	$13.362	$13.36	$13.35	$13.40
Purchase #2	$63.28	5.274%	$66.6174	$66.62	$66.60	$66.60
Purchase #3	$189.41	10.634%	$209.5519	$209.55	$209.55	$209.60
Purchase #4	$105.81	5.176%	$111.2867	$111.29	$111.30	$111.30
Purchase #5	$147.87	4.214%	$154.1012	$154.10	$154.10	$154.10
Purchase #6	$118.76	10.561%	$131.3022	$131.30	$131.30	$131.30
Purchase #7	$48.32	4.858%	$50.6674	$50.67	$50.65	$50.70
7 purchase totals =	$686.22		$736.8888	$736.89	$736.85	$737.00