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	$43.48	10.249%	$47.9363	$47.94	$47.95	$47.90
Purchase #2	$46.87	8.397%	$50.8057	$50.81	$50.80	$50.80
Purchase #3	$138.30	5.835%	$146.3698	$146.37	$146.35	$146.40
Purchase #4	$51.71	13.265%	$58.5693	$58.57	$58.55	$58.60
Purchase #5	$100.35	5.152%	$105.52	$105.52	$105.50	$105.50
Purchase #6	$74.33	8.162%	$80.3968	$80.40	$80.40	$80.40
Purchase #7	$71.28	10.630%	$78.8571	$78.86	$78.85	$78.90
7 purchase totals =	$526.32		$568.4550	$568.47	$568.40	$568.50