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	$29.89	11.184%	$33.2329	$33.23	$33.25	$33.20
Purchase #2	$70.98	8.534%	$77.0374	$77.04	$77.05	$77.00
Purchase #3	$139.49	13.671%	$158.5597	$158.56	$158.55	$158.60
Purchase #4	$41.85	4.521%	$43.742	$43.74	$43.75	$43.70
Purchase #5	$5.93	9.121%	$6.4709	$6.47	$6.45	$6.50
Purchase #6	$98.75	12.713%	$111.3041	$111.30	$111.30	$111.30
Purchase #7	$48.94	11.763%	$54.6968	$54.70	$54.70	$54.70
7 purchase totals =	$435.83		$485.0438	$485.04	$485.05	$485.00