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	$241.30	6.145%	$256.1279	$256.13	$256.15	$256.10
Purchase #2	$104.94	6.164%	$111.4085	$111.41	$111.40	$111.40
Purchase #3	$210.91	8.716%	$229.2929	$229.29	$229.30	$229.30
Purchase #4	$176.78	12.815%	$199.4344	$199.43	$199.45	$199.40
Purchase #5	$20.55	12.544%	$23.1278	$23.13	$23.15	$23.10
Purchase #6	$7.98	7.321%	$8.5642	$8.56	$8.55	$8.60
Purchase #7	$112.42	3.411%	$116.2546	$116.25	$116.25	$116.30
7 purchase totals =	$874.88		$944.2103	$944.20	$944.25	$944.20