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	$118.66	6.611%	$126.5046	$126.50	$126.50	$126.50
Purchase #2	$168.94	7.594%	$181.7693	$181.77	$181.75	$181.80
Purchase #3	$150.71	11.806%	$168.5028	$168.50	$168.50	$168.50
Purchase #4	$74.64	12.293%	$83.8155	$83.82	$83.80	$83.80
Purchase #5	$198.68	13.714%	$225.927	$225.93	$225.95	$225.90
Purchase #6	$175.79	4.176%	$183.131	$183.13	$183.15	$183.10
Purchase #7	$33.60	5.537%	$35.4604	$35.46	$35.45	$35.50
7 purchase totals =	$921.02		$1,005.1106	$1,005.11	$1,005.10	$1,005.10