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	$75.88	8.814%	$82.5681	$82.57	$82.55	$82.60
Purchase #2	$175.46	8.256%	$189.946	$189.95	$189.95	$189.90
Purchase #3	$243.61	3.696%	$252.6138	$252.61	$252.60	$252.60
Purchase #4	$187.85	11.568%	$209.5805	$209.58	$209.60	$209.60
Purchase #5	$10.99	11.491%	$12.2529	$12.25	$12.25	$12.30
Purchase #6	$98.68	13.424%	$111.9268	$111.93	$111.95	$111.90
Purchase #7	$183.77	3.680%	$190.5327	$190.53	$190.55	$190.50
7 purchase totals =	$976.24		$1,049.4208	$1,049.42	$1,049.45	$1,049.40