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	$111.29	13.277%	$126.066	$126.07	$126.05	$126.10
Purchase #2	$26.59	12.197%	$29.8332	$29.83	$29.85	$29.80
Purchase #3	$48.37	9.308%	$52.8723	$52.87	$52.85	$52.90
Purchase #4	$55.48	5.621%	$58.5985	$58.60	$58.60	$58.60
Purchase #5	$96.55	9.353%	$105.5803	$105.58	$105.60	$105.60
Purchase #6	$106.47	5.544%	$112.3727	$112.37	$112.35	$112.40
Purchase #7	$134.78	7.766%	$145.247	$145.25	$145.25	$145.20
7 purchase totals =	$579.53		$630.5700	$630.57	$630.55	$630.60