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	$214.77	12.327%	$241.2447	$241.24	$241.25	$241.20
Purchase #2	$26.40	8.670%	$28.6889	$28.69	$28.70	$28.70
Purchase #3	$88.95	13.371%	$100.8435	$100.84	$100.85	$100.80
Purchase #4	$193.26	11.407%	$215.3052	$215.31	$215.30	$215.30
Purchase #5	$189.83	10.509%	$209.7792	$209.78	$209.80	$209.80
Purchase #6	$247.61	9.826%	$271.9402	$271.94	$271.95	$271.90
Purchase #7	$42.26	3.472%	$43.7273	$43.73	$43.75	$43.70
7 purchase totals =	$1,003.08		$1,111.5290	$1,111.53	$1,111.60	$1,111.40