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	$9.43	11.587%	$10.5227	$10.52	$10.50	$10.50
Purchase #2	$171.91	3.742%	$178.3429	$178.34	$178.35	$178.30
Purchase #3	$89.34	4.521%	$93.3791	$93.38	$93.40	$93.40
Purchase #4	$61.78	7.707%	$66.5414	$66.54	$66.55	$66.50
Purchase #5	$34.63	12.224%	$38.8632	$38.86	$38.85	$38.90
Purchase #6	$88.39	7.536%	$95.0511	$95.05	$95.05	$95.10
Purchase #7	$190.89	11.391%	$212.6343	$212.63	$212.65	$212.60
7 purchase totals =	$646.37		$695.3347	$695.32	$695.35	$695.30