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	$133.52	7.597%	$143.6635	$143.66	$143.65	$143.70
Purchase #2	$31.94	10.328%	$35.2388	$35.24	$35.25	$35.20
Purchase #3	$88.30	8.434%	$95.7472	$95.75	$95.75	$95.70
Purchase #4	$38.59	4.203%	$40.2119	$40.21	$40.20	$40.20
Purchase #5	$66.94	8.533%	$72.652	$72.65	$72.65	$72.70
Purchase #6	$93.71	10.330%	$103.3902	$103.39	$103.40	$103.40
Purchase #7	$20.79	5.160%	$21.8628	$21.86	$21.85	$21.90
7 purchase totals =	$473.79		$512.7664	$512.76	$512.75	$512.80