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	$112.85	9.648%	$123.7378	$123.74	$123.75	$123.70
Purchase #2	$47.68	13.116%	$53.9337	$53.93	$53.95	$53.90
Purchase #3	$107.27	4.276%	$111.8569	$111.86	$111.85	$111.90
Purchase #4	$188.80	6.247%	$200.5943	$200.59	$200.60	$200.60
Purchase #5	$81.43	6.540%	$86.7555	$86.76	$86.75	$86.80
Purchase #6	$138.45	7.597%	$148.968	$148.97	$148.95	$149.00
Purchase #7	$188.82	7.725%	$203.4063	$203.41	$203.40	$203.40
7 purchase totals =	$865.30		$929.2525	$929.26	$929.25	$929.30