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	$241.71	8.507%	$262.2723	$262.27	$262.25	$262.30
Purchase #2	$129.74	10.847%	$143.8129	$143.81	$143.80	$143.80
Purchase #3	$73.85	12.434%	$83.0325	$83.03	$83.05	$83.00
Purchase #4	$36.29	13.719%	$41.2686	$41.27	$41.25	$41.30
Purchase #5	$66.63	6.830%	$71.1808	$71.18	$71.20	$71.20
Purchase #6	$184.58	11.213%	$205.277	$205.28	$205.30	$205.30
Purchase #7	$128.70	12.153%	$144.3409	$144.34	$144.35	$144.30
7 purchase totals =	$861.50		$951.1850	$951.18	$951.20	$951.20