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	$113.94	4.611%	$119.1938	$119.19	$119.20	$119.20
Purchase #2	$108.78	8.273%	$117.7794	$117.78	$117.80	$117.80
Purchase #3	$12.32	4.708%	$12.9	$12.90	$12.90	$12.90
Purchase #4	$13.36	10.181%	$14.7202	$14.72	$14.70	$14.70
Purchase #5	$92.81	13.423%	$105.2679	$105.27	$105.25	$105.30
Purchase #6	$47.84	10.425%	$52.8273	$52.83	$52.85	$52.80
Purchase #7	$179.56	9.552%	$196.7116	$196.71	$196.70	$196.70
7 purchase totals =	$568.61		$619.4002	$619.40	$619.40	$619.40