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	$39.95	4.758%	$41.8508	$41.85	$41.85	$41.90
Purchase #2	$232.59	3.459%	$240.6353	$240.64	$240.65	$240.60
Purchase #3	$226.52	12.863%	$255.6573	$255.66	$255.65	$255.70
Purchase #4	$56.58	8.691%	$61.4974	$61.50	$61.50	$61.50
Purchase #5	$108.61	10.676%	$120.2052	$120.21	$120.20	$120.20
Purchase #6	$119.73	6.660%	$127.704	$127.70	$127.70	$127.70
Purchase #7	$92.44	12.423%	$103.9238	$103.92	$103.90	$103.90
7 purchase totals =	$876.42		$951.4738	$951.48	$951.45	$951.50