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	$105.27	8.186%	$113.8874	$113.89	$113.90	$113.90
Purchase #2	$207.33	8.708%	$225.3843	$225.38	$225.40	$225.40
Purchase #3	$29.62	12.359%	$33.2807	$33.28	$33.30	$33.30
Purchase #4	$55.82	11.851%	$62.4352	$62.44	$62.45	$62.40
Purchase #5	$192.45	3.660%	$199.4937	$199.49	$199.50	$199.50
Purchase #6	$136.55	10.505%	$150.8946	$150.89	$150.90	$150.90
Purchase #7	$152.88	13.852%	$174.0569	$174.06	$174.05	$174.10
7 purchase totals =	$879.92		$959.4328	$959.43	$959.50	$959.50