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	$174.93	3.175%	$180.484	$180.48	$180.50	$180.50
Purchase #2	$189.26	13.543%	$214.8915	$214.89	$214.90	$214.90
Purchase #3	$225.56	11.858%	$252.3069	$252.31	$252.30	$252.30
Purchase #4	$41.32	4.294%	$43.0943	$43.09	$43.10	$43.10
Purchase #5	$32.52	12.332%	$36.5304	$36.53	$36.55	$36.50
Purchase #6	$246.96	6.845%	$263.8644	$263.86	$263.85	$263.90
Purchase #7	$118.88	11.556%	$132.6178	$132.62	$132.60	$132.60
7 purchase totals =	$1,029.43		$1,123.7893	$1,123.78	$1,123.80	$1,123.80