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	$177.98	6.774%	$190.0364	$190.04	$190.05	$190.00
Purchase #2	$240.58	9.484%	$263.3966	$263.40	$263.40	$263.40
Purchase #3	$40.82	10.405%	$45.0673	$45.07	$45.05	$45.10
Purchase #4	$62.95	5.534%	$66.4337	$66.43	$66.45	$66.40
Purchase #5	$159.68	9.343%	$174.5989	$174.60	$174.60	$174.60
Purchase #6	$119.83	10.546%	$132.4673	$132.47	$132.45	$132.50
Purchase #7	$28.83	9.235%	$31.4925	$31.49	$31.50	$31.50
7 purchase totals =	$830.67		$903.4927	$903.50	$903.50	$903.50