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	$183.80	3.527%	$190.2826	$190.28	$190.30	$190.30
Purchase #2	$140.61	13.358%	$159.3927	$159.39	$159.40	$159.40
Purchase #3	$206.55	11.605%	$230.5201	$230.52	$230.50	$230.50
Purchase #4	$62.90	6.335%	$66.8847	$66.88	$66.90	$66.90
Purchase #5	$105.26	12.577%	$118.4986	$118.50	$118.50	$118.50
Purchase #6	$188.57	9.627%	$206.7236	$206.72	$206.70	$206.70
Purchase #7	$136.95	5.172%	$144.0331	$144.03	$144.05	$144.00
7 purchase totals =	$1,024.64		$1,116.3354	$1,116.32	$1,116.35	$1,116.30