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	$104.97	8.526%	$113.9197	$113.92	$113.90	$113.90
Purchase #2	$97.52	12.389%	$109.6018	$109.60	$109.60	$109.60
Purchase #3	$104.54	13.187%	$118.3257	$118.33	$118.35	$118.30
Purchase #4	$119.47	3.259%	$123.3635	$123.36	$123.35	$123.40
Purchase #5	$100.63	10.864%	$111.5624	$111.56	$111.55	$111.60
Purchase #6	$218.50	5.845%	$231.2713	$231.27	$231.25	$231.30
Purchase #7	$117.53	3.664%	$121.8363	$121.84	$121.85	$121.80
7 purchase totals =	$863.16		$929.8807	$929.88	$929.85	$929.90