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	$68.98	13.149%	$78.0502	$78.05	$78.05	$78.10
Purchase #2	$128.45	4.789%	$134.6015	$134.60	$134.60	$134.60
Purchase #3	$103.65	13.385%	$117.5236	$117.52	$117.50	$117.50
Purchase #4	$150.49	13.297%	$170.5007	$170.50	$170.50	$170.50
Purchase #5	$112.80	13.577%	$128.1149	$128.11	$128.10	$128.10
Purchase #6	$59.55	11.603%	$66.4596	$66.46	$66.45	$66.50
Purchase #7	$214.83	11.314%	$239.1359	$239.14	$239.15	$239.10
7 purchase totals =	$838.75		$934.3864	$934.38	$934.35	$934.40