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	$42.78	8.509%	$46.4202	$46.42	$46.40	$46.40
Purchase #2	$246.44	13.269%	$279.1401	$279.14	$279.15	$279.10
Purchase #3	$128.29	11.449%	$142.9779	$142.98	$143.00	$143.00
Purchase #4	$175.94	8.475%	$190.8509	$190.85	$190.85	$190.90
Purchase #5	$97.71	6.186%	$103.7543	$103.75	$103.75	$103.80
Purchase #6	$140.77	9.122%	$153.611	$153.61	$153.60	$153.60
Purchase #7	$234.57	7.282%	$251.6514	$251.65	$251.65	$251.70
7 purchase totals =	$1,066.50		$1,168.4058	$1,168.40	$1,168.40	$1,168.50