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	$101.75	9.331%	$111.2443	$111.24	$111.25	$111.20
Purchase #2	$5.30	5.426%	$5.5876	$5.59	$5.60	$5.60
Purchase #3	$34.50	3.800%	$35.811	$35.81	$35.80	$35.80
Purchase #4	$136.27	10.489%	$150.5634	$150.56	$150.55	$150.60
Purchase #5	$78.46	11.612%	$87.5708	$87.57	$87.55	$87.60
Purchase #6	$60.67	9.725%	$66.5702	$66.57	$66.55	$66.60
Purchase #7	$200.99	12.404%	$225.9208	$225.92	$225.90	$225.90
7 purchase totals =	$617.94		$683.2681	$683.26	$683.20	$683.30