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	$212.70	13.723%	$241.8888	$241.89	$241.90	$241.90
Purchase #2	$121.47	11.512%	$135.4536	$135.45	$135.45	$135.50
Purchase #3	$195.51	10.226%	$215.5029	$215.50	$215.50	$215.50
Purchase #4	$59.87	5.392%	$63.0982	$63.10	$63.10	$63.10
Purchase #5	$145.64	5.417%	$153.5293	$153.53	$153.55	$153.50
Purchase #6	$209.64	13.856%	$238.6877	$238.69	$238.70	$238.70
Purchase #7	$122.76	4.108%	$127.803	$127.80	$127.80	$127.80
7 purchase totals =	$1,067.59		$1,175.9635	$1,175.96	$1,176.00	$1,176.00