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	$114.95	8.786%	$125.0495	$125.05	$125.05	$125.00
Purchase #2	$61.51	13.205%	$69.6324	$69.63	$69.65	$69.60
Purchase #3	$95.66	10.347%	$105.5579	$105.56	$105.55	$105.60
Purchase #4	$242.75	5.390%	$255.8342	$255.83	$255.85	$255.80
Purchase #5	$118.51	10.339%	$130.7627	$130.76	$130.75	$130.80
Purchase #6	$13.79	6.166%	$14.6403	$14.64	$14.65	$14.60
Purchase #7	$90.28	11.657%	$100.8039	$100.80	$100.80	$100.80
7 purchase totals =	$737.45		$802.2809	$802.27	$802.30	$802.20