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	$226.75	10.294%	$250.0916	$250.09	$250.10	$250.10
Purchase #2	$57.36	11.323%	$63.8549	$63.85	$63.85	$63.90
Purchase #3	$156.77	7.663%	$168.7833	$168.78	$168.80	$168.80
Purchase #4	$203.40	13.291%	$230.4339	$230.43	$230.45	$230.40
Purchase #5	$100.60	9.863%	$110.5222	$110.52	$110.50	$110.50
Purchase #6	$208.52	3.153%	$215.0946	$215.09	$215.10	$215.10
Purchase #7	$43.95	6.277%	$46.7087	$46.71	$46.70	$46.70
7 purchase totals =	$997.35		$1,085.4892	$1,085.47	$1,085.50	$1,085.50