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	$161.78	8.504%	$175.5378	$175.54	$175.55	$175.50
Purchase #2	$130.72	6.272%	$138.9188	$138.92	$138.90	$138.90
Purchase #3	$174.57	4.465%	$182.3646	$182.36	$182.35	$182.40
Purchase #4	$51.34	3.338%	$53.0537	$53.05	$53.05	$53.10
Purchase #5	$50.89	10.588%	$56.2782	$56.28	$56.30	$56.30
Purchase #6	$108.60	13.475%	$123.2339	$123.23	$123.25	$123.20
Purchase #7	$244.51	11.533%	$272.7093	$272.71	$272.70	$272.70
7 purchase totals =	$922.41		$1,002.0963	$1,002.09	$1,002.10	$1,002.10