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	$189.50	13.796%	$215.6434	$215.64	$215.65	$215.60
Purchase #2	$57.61	8.650%	$62.5933	$62.59	$62.60	$62.60
Purchase #3	$245.77	8.851%	$267.5231	$267.52	$267.50	$267.50
Purchase #4	$152.59	13.806%	$173.6566	$173.66	$173.65	$173.70
Purchase #5	$174.47	7.472%	$187.5064	$187.51	$187.50	$187.50
Purchase #6	$233.95	10.680%	$258.9359	$258.94	$258.95	$258.90
Purchase #7	$169.53	10.719%	$187.7019	$187.70	$187.70	$187.70
7 purchase totals =	$1,223.42		$1,353.5606	$1,353.56	$1,353.55	$1,353.50