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	$204.92	6.189%	$217.6025	$217.60	$217.60	$217.60
Purchase #2	$204.40	10.517%	$225.8967	$225.90	$225.90	$225.90
Purchase #3	$19.65	7.141%	$21.0532	$21.05	$21.05	$21.10
Purchase #4	$182.89	4.576%	$191.259	$191.26	$191.25	$191.30
Purchase #5	$81.86	8.828%	$89.0866	$89.09	$89.10	$89.10
Purchase #6	$133.70	13.198%	$151.3457	$151.35	$151.35	$151.30
Purchase #7	$150.90	3.446%	$156.1	$156.10	$156.10	$156.10
7 purchase totals =	$978.32		$1,052.3437	$1,052.35	$1,052.35	$1,052.40