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	$128.64	9.241%	$140.5276	$140.53	$140.55	$140.50
Purchase #2	$50.78	13.550%	$57.6607	$57.66	$57.65	$57.70
Purchase #3	$172.94	13.841%	$196.8766	$196.88	$196.90	$196.90
Purchase #4	$177.69	12.180%	$199.3326	$199.33	$199.35	$199.30
Purchase #5	$224.29	4.683%	$234.7935	$234.79	$234.80	$234.80
Purchase #6	$46.94	4.181%	$48.9026	$48.90	$48.90	$48.90
Purchase #7	$248.57	11.361%	$276.81	$276.81	$276.80	$276.80
7 purchase totals =	$1,049.85		$1,154.9036	$1,154.90	$1,154.95	$1,154.90