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	$95.99	7.831%	$103.507	$103.51	$103.50	$103.50
Purchase #2	$216.53	10.573%	$239.4237	$239.42	$239.40	$239.40
Purchase #3	$190.71	7.721%	$205.4347	$205.43	$205.45	$205.40
Purchase #4	$118.55	7.671%	$127.644	$127.64	$127.65	$127.60
Purchase #5	$183.60	3.792%	$190.5621	$190.56	$190.55	$190.60
Purchase #6	$109.29	12.229%	$122.6551	$122.66	$122.65	$122.70
Purchase #7	$194.96	13.505%	$221.2893	$221.29	$221.30	$221.30
7 purchase totals =	$1,109.63		$1,210.5159	$1,210.51	$1,210.50	$1,210.50