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	$115.65	9.453%	$126.5824	$126.58	$126.60	$126.60
Purchase #2	$63.86	13.522%	$72.4951	$72.50	$72.50	$72.50
Purchase #3	$248.98	5.429%	$262.4971	$262.50	$262.50	$262.50
Purchase #4	$141.99	6.240%	$150.8502	$150.85	$150.85	$150.90
Purchase #5	$81.54	6.305%	$86.6811	$86.68	$86.70	$86.70
Purchase #6	$53.85	3.744%	$55.8661	$55.87	$55.85	$55.90
Purchase #7	$42.39	12.344%	$47.6226	$47.62	$47.60	$47.60
7 purchase totals =	$748.26		$802.5946	$802.60	$802.60	$802.70