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	$14.81	13.662%	$16.8333	$16.83	$16.85	$16.80
Purchase #2	$65.99	10.598%	$72.9836	$72.98	$73.00	$73.00
Purchase #3	$227.28	12.587%	$255.8877	$255.89	$255.90	$255.90
Purchase #4	$181.82	13.730%	$206.7839	$206.78	$206.80	$206.80
Purchase #5	$141.92	9.485%	$155.3811	$155.38	$155.40	$155.40
Purchase #6	$137.81	10.821%	$152.7224	$152.72	$152.70	$152.70
Purchase #7	$166.80	3.512%	$172.658	$172.66	$172.65	$172.70
7 purchase totals =	$936.43		$1,033.2500	$1,033.24	$1,033.30	$1,033.30