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	$44.66	9.329%	$48.8263	$48.83	$48.85	$48.80
Purchase #2	$177.37	12.835%	$200.1354	$200.14	$200.15	$200.10
Purchase #3	$210.31	7.235%	$225.5259	$225.53	$225.55	$225.50
Purchase #4	$44.93	9.530%	$49.2118	$49.21	$49.20	$49.20
Purchase #5	$222.58	13.156%	$251.8626	$251.86	$251.85	$251.90
Purchase #6	$37.95	11.288%	$42.2338	$42.23	$42.25	$42.20
Purchase #7	$104.51	11.870%	$116.9153	$116.92	$116.90	$116.90
7 purchase totals =	$842.31		$934.7111	$934.72	$934.75	$934.60