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	$142.85	3.627%	$148.0312	$148.03	$148.05	$148.00
Purchase #2	$106.66	5.739%	$112.7812	$112.78	$112.80	$112.80
Purchase #3	$127.67	10.467%	$141.0332	$141.03	$141.05	$141.00
Purchase #4	$77.65	3.440%	$80.3212	$80.32	$80.30	$80.30
Purchase #5	$62.93	5.353%	$66.2986	$66.30	$66.30	$66.30
Purchase #6	$117.28	11.748%	$131.0581	$131.06	$131.05	$131.10
Purchase #7	$138.73	10.679%	$153.545	$153.55	$153.55	$153.50
7 purchase totals =	$773.77		$833.0685	$833.07	$833.10	$833.00