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	$211.70	12.645%	$238.4695	$238.47	$238.45	$238.50
Purchase #2	$35.88	12.867%	$40.4967	$40.50	$40.50	$40.50
Purchase #3	$241.55	12.390%	$271.478	$271.48	$271.50	$271.50
Purchase #4	$48.75	13.720%	$55.4385	$55.44	$55.45	$55.40
Purchase #5	$87.88	12.212%	$98.6119	$98.61	$98.60	$98.60
Purchase #6	$202.65	13.625%	$230.2611	$230.26	$230.25	$230.30
Purchase #7	$95.39	5.464%	$100.6021	$100.60	$100.60	$100.60
7 purchase totals =	$923.80		$1,035.3578	$1,035.36	$1,035.35	$1,035.40