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	$48.45	7.447%	$52.0581	$52.06	$52.05	$52.10
Purchase #2	$143.62	11.156%	$159.6422	$159.64	$159.65	$159.60
Purchase #3	$201.78	3.781%	$209.4093	$209.41	$209.40	$209.40
Purchase #4	$38.77	4.714%	$40.5976	$40.60	$40.60	$40.60
Purchase #5	$43.74	10.345%	$48.2649	$48.26	$48.25	$48.30
Purchase #6	$57.75	6.163%	$61.3091	$61.31	$61.30	$61.30
Purchase #7	$194.46	11.626%	$217.0679	$217.07	$217.05	$217.10
7 purchase totals =	$728.57		$788.3491	$788.35	$788.30	$788.40