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	$66.76	7.247%	$71.5981	$71.60	$71.60	$71.60
Purchase #2	$135.58	7.292%	$145.4665	$145.47	$145.45	$145.50
Purchase #3	$231.58	4.124%	$241.1304	$241.13	$241.15	$241.10
Purchase #4	$209.31	8.789%	$227.7063	$227.71	$227.70	$227.70
Purchase #5	$49.82	11.863%	$55.7301	$55.73	$55.75	$55.70
Purchase #6	$231.38	11.733%	$258.5278	$258.53	$258.55	$258.50
Purchase #7	$91.54	13.136%	$103.5647	$103.56	$103.55	$103.60
7 purchase totals =	$1,015.97		$1,103.7239	$1,103.73	$1,103.75	$1,103.70