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	$149.40	3.790%	$155.0623	$155.06	$155.05	$155.10
Purchase #2	$169.91	8.446%	$184.2606	$184.26	$184.25	$184.30
Purchase #3	$112.72	3.646%	$116.8298	$116.83	$116.85	$116.80
Purchase #4	$31.73	8.245%	$34.3461	$34.35	$34.35	$34.30
Purchase #5	$148.73	3.784%	$154.3579	$154.36	$154.35	$154.40
Purchase #6	$48.30	4.410%	$50.43	$50.43	$50.45	$50.40
Purchase #7	$53.41	10.715%	$59.1329	$59.13	$59.15	$59.10
7 purchase totals =	$714.20		$754.4196	$754.42	$754.45	$754.40