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	$112.63	13.354%	$127.6706	$127.67	$127.65	$127.70
Purchase #2	$53.50	12.545%	$60.2116	$60.21	$60.20	$60.20
Purchase #3	$172.83	10.433%	$190.8614	$190.86	$190.85	$190.90
Purchase #4	$160.42	13.359%	$181.8505	$181.85	$181.85	$181.90
Purchase #5	$111.35	12.397%	$125.1541	$125.15	$125.15	$125.20
Purchase #6	$240.87	8.567%	$261.5053	$261.51	$261.50	$261.50
Purchase #7	$155.66	5.216%	$163.7792	$163.78	$163.80	$163.80
7 purchase totals =	$1,007.26		$1,111.0327	$1,111.03	$1,111.00	$1,111.20