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	$155.29	6.491%	$165.3699	$165.37	$165.35	$165.40
Purchase #2	$126.53	3.729%	$131.2483	$131.25	$131.25	$131.20
Purchase #3	$32.81	9.164%	$35.8167	$35.82	$35.80	$35.80
Purchase #4	$42.93	5.559%	$45.3165	$45.32	$45.30	$45.30
Purchase #5	$74.38	12.863%	$83.9475	$83.95	$83.95	$83.90
Purchase #6	$59.89	5.684%	$63.2941	$63.29	$63.30	$63.30
Purchase #7	$170.83	4.484%	$178.49	$178.49	$178.50	$178.50
7 purchase totals =	$662.66		$703.4830	$703.49	$703.45	$703.40