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	$217.52	11.367%	$242.2455	$242.25	$242.25	$242.20
Purchase #2	$87.27	13.280%	$98.8595	$98.86	$98.85	$98.90
Purchase #3	$41.27	7.240%	$44.2579	$44.26	$44.25	$44.30
Purchase #4	$80.44	3.598%	$83.3342	$83.33	$83.35	$83.30
Purchase #5	$81.85	11.110%	$90.9435	$90.94	$90.95	$90.90
Purchase #6	$127.97	10.242%	$141.0767	$141.08	$141.10	$141.10
Purchase #7	$169.39	4.225%	$176.5467	$176.55	$176.55	$176.50
7 purchase totals =	$805.71		$877.2640	$877.27	$877.30	$877.20