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	$241.59	7.138%	$258.8347	$258.83	$258.85	$258.80
Purchase #2	$87.47	11.869%	$97.8518	$97.85	$97.85	$97.90
Purchase #3	$127.72	8.536%	$138.6222	$138.62	$138.60	$138.60
Purchase #4	$148.29	12.616%	$166.9983	$167.00	$167.00	$167.00
Purchase #5	$157.50	6.702%	$168.0557	$168.06	$168.05	$168.10
Purchase #6	$155.86	12.693%	$175.6433	$175.64	$175.65	$175.60
Purchase #7	$229.97	11.576%	$256.5913	$256.59	$256.60	$256.60
7 purchase totals =	$1,148.40		$1,262.5973	$1,262.59	$1,262.60	$1,262.60