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	$105.94	12.203%	$118.8679	$118.87	$118.85	$118.90
Purchase #2	$45.90	4.474%	$47.9536	$47.95	$47.95	$48.00
Purchase #3	$121.35	8.372%	$131.5094	$131.51	$131.50	$131.50
Purchase #4	$212.71	13.194%	$240.775	$240.78	$240.80	$240.80
Purchase #5	$179.77	11.547%	$200.528	$200.53	$200.55	$200.50
Purchase #6	$138.81	5.764%	$146.811	$146.81	$146.80	$146.80
Purchase #7	$86.27	11.307%	$96.0245	$96.02	$96.00	$96.00
7 purchase totals =	$890.75		$982.4694	$982.47	$982.45	$982.50