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	$207.36	13.715%	$235.7994	$235.80	$235.80	$235.80
Purchase #2	$68.45	5.732%	$72.3736	$72.37	$72.35	$72.40
Purchase #3	$99.47	5.737%	$105.1766	$105.18	$105.20	$105.20
Purchase #4	$157.87	5.417%	$166.4218	$166.42	$166.40	$166.40
Purchase #5	$125.31	11.758%	$140.0439	$140.04	$140.05	$140.00
Purchase #6	$127.55	7.526%	$137.1494	$137.15	$137.15	$137.10
Purchase #7	$36.57	13.630%	$41.5545	$41.55	$41.55	$41.60
7 purchase totals =	$822.58		$898.5192	$898.51	$898.50	$898.50