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	$233.71	10.780%	$258.9039	$258.90	$258.90	$258.90
Purchase #2	$11.63	8.665%	$12.6377	$12.64	$12.65	$12.60
Purchase #3	$161.40	11.552%	$180.0449	$180.04	$180.05	$180.00
Purchase #4	$124.90	5.760%	$132.0942	$132.09	$132.10	$132.10
Purchase #5	$231.94	10.292%	$255.8113	$255.81	$255.80	$255.80
Purchase #6	$43.27	4.138%	$45.0605	$45.06	$45.05	$45.10
Purchase #7	$59.84	10.792%	$66.2979	$66.30	$66.30	$66.30
7 purchase totals =	$866.69		$950.8504	$950.84	$950.85	$950.80