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	$125.42	11.255%	$139.536	$139.54	$139.55	$139.50
Purchase #2	$12.74	11.408%	$14.1934	$14.19	$14.20	$14.20
Purchase #3	$165.92	6.331%	$176.4244	$176.42	$176.40	$176.40
Purchase #4	$133.70	8.328%	$144.8345	$144.83	$144.85	$144.80
Purchase #5	$116.45	6.336%	$123.8283	$123.83	$123.85	$123.80
Purchase #6	$161.32	10.871%	$178.8571	$178.86	$178.85	$178.90
Purchase #7	$156.97	10.778%	$173.8882	$173.89	$173.90	$173.90
7 purchase totals =	$872.52		$951.5619	$951.56	$951.60	$951.50