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	$204.54	11.368%	$227.7921	$227.79	$227.80	$227.80
Purchase #2	$63.46	13.573%	$72.0734	$72.07	$72.05	$72.10
Purchase #3	$207.25	3.737%	$214.9949	$214.99	$215.00	$215.00
Purchase #4	$139.90	6.228%	$148.613	$148.61	$148.60	$148.60
Purchase #5	$24.84	4.241%	$25.8935	$25.89	$25.90	$25.90
Purchase #6	$111.47	11.144%	$123.8922	$123.89	$123.90	$123.90
Purchase #7	$182.90	8.332%	$198.1392	$198.14	$198.15	$198.10
7 purchase totals =	$934.36		$1,011.3983	$1,011.38	$1,011.40	$1,011.40