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	$233.33	11.134%	$259.309	$259.31	$259.30	$259.30
Purchase #2	$45.39	5.472%	$47.8737	$47.87	$47.85	$47.90
Purchase #3	$207.55	9.823%	$227.9376	$227.94	$227.95	$227.90
Purchase #4	$104.86	3.309%	$108.3298	$108.33	$108.35	$108.30
Purchase #5	$20.47	6.783%	$21.8585	$21.86	$21.85	$21.90
Purchase #6	$103.53	8.622%	$112.4564	$112.46	$112.45	$112.50
Purchase #7	$40.33	5.437%	$42.5227	$42.52	$42.50	$42.50
7 purchase totals =	$755.46		$820.2877	$820.29	$820.25	$820.30