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	$95.79	4.340%	$99.9473	$99.95	$99.95	$99.90
Purchase #2	$63.48	11.517%	$70.791	$70.79	$70.80	$70.80
Purchase #3	$146.64	3.153%	$151.2636	$151.26	$151.25	$151.30
Purchase #4	$210.91	3.212%	$217.6844	$217.68	$217.70	$217.70
Purchase #5	$112.90	9.782%	$123.9439	$123.94	$123.95	$123.90
Purchase #6	$51.27	7.115%	$54.9179	$54.92	$54.90	$54.90
Purchase #7	$222.66	8.406%	$241.3768	$241.38	$241.40	$241.40
7 purchase totals =	$903.65		$959.9249	$959.92	$959.95	$959.90