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	$42.34	12.709%	$47.721	$47.72	$47.70	$47.70
Purchase #2	$198.32	13.870%	$225.827	$225.83	$225.85	$225.80
Purchase #3	$65.52	8.627%	$71.1724	$71.17	$71.15	$71.20
Purchase #4	$140.78	3.321%	$145.4553	$145.46	$145.45	$145.50
Purchase #5	$174.70	12.397%	$196.3576	$196.36	$196.35	$196.40
Purchase #6	$151.66	4.382%	$158.3057	$158.31	$158.30	$158.30
Purchase #7	$49.54	13.562%	$56.2586	$56.26	$56.25	$56.30
7 purchase totals =	$822.86		$901.0976	$901.11	$901.05	$901.20