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	$107.68	11.121%	$119.6551	$119.66	$119.65	$119.70
Purchase #2	$28.82	6.291%	$30.6331	$30.63	$30.65	$30.60
Purchase #3	$81.26	9.609%	$89.0683	$89.07	$89.05	$89.10
Purchase #4	$204.45	11.322%	$227.5978	$227.60	$227.60	$227.60
Purchase #5	$100.26	13.158%	$113.4522	$113.45	$113.45	$113.50
Purchase #6	$164.32	4.562%	$171.8163	$171.82	$171.80	$171.80
Purchase #7	$246.83	11.778%	$275.9016	$275.90	$275.90	$275.90
7 purchase totals =	$933.62		$1,028.1244	$1,028.13	$1,028.10	$1,028.20