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	$185.52	12.610%	$208.9141	$208.91	$208.90	$208.90
Purchase #2	$11.42	6.755%	$12.1914	$12.19	$12.20	$12.20
Purchase #3	$41.64	12.657%	$46.9104	$46.91	$46.90	$46.90
Purchase #4	$157.69	6.683%	$168.2284	$168.23	$168.25	$168.20
Purchase #5	$16.64	9.322%	$18.1912	$18.19	$18.20	$18.20
Purchase #6	$41.47	3.282%	$42.831	$42.83	$42.85	$42.80
Purchase #7	$197.38	12.193%	$221.4465	$221.45	$221.45	$221.40
7 purchase totals =	$651.76		$718.7130	$718.71	$718.75	$718.60