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	$116.45	5.131%	$122.425	$122.43	$122.45	$122.40
Purchase #2	$93.31	11.158%	$103.7215	$103.72	$103.70	$103.70
Purchase #3	$121.38	4.680%	$127.0606	$127.06	$127.05	$127.10
Purchase #4	$106.90	5.418%	$112.6918	$112.69	$112.70	$112.70
Purchase #5	$57.50	10.157%	$63.3403	$63.34	$63.35	$63.30
Purchase #6	$142.32	3.253%	$146.9497	$146.95	$146.95	$146.90
Purchase #7	$108.60	13.329%	$123.0753	$123.08	$123.10	$123.10
7 purchase totals =	$746.46		$799.2642	$799.27	$799.30	$799.20