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	$174.31	3.185%	$179.8618	$179.86	$179.85	$179.90
Purchase #2	$87.29	3.783%	$90.5922	$90.59	$90.60	$90.60
Purchase #3	$177.82	10.649%	$196.7561	$196.76	$196.75	$196.80
Purchase #4	$80.34	10.351%	$88.656	$88.66	$88.65	$88.70
Purchase #5	$217.45	4.423%	$227.0678	$227.07	$227.05	$227.10
Purchase #6	$138.71	3.341%	$143.3443	$143.34	$143.35	$143.30
Purchase #7	$5.39	6.788%	$5.7559	$5.76	$5.75	$5.80
7 purchase totals =	$881.31		$932.0341	$932.04	$932.00	$932.20