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	$65.60	8.386%	$71.1012	$71.10	$71.10	$71.10
Purchase #2	$28.73	13.716%	$32.6706	$32.67	$32.65	$32.70
Purchase #3	$6.28	5.145%	$6.6031	$6.60	$6.60	$6.60
Purchase #4	$25.27	10.264%	$27.8637	$27.86	$27.85	$27.90
Purchase #5	$182.44	7.757%	$196.5919	$196.59	$196.60	$196.60
Purchase #6	$112.63	4.457%	$117.6499	$117.65	$117.65	$117.60
Purchase #7	$16.28	4.292%	$16.9787	$16.98	$17.00	$17.00
7 purchase totals =	$437.23		$469.4591	$469.45	$469.45	$469.50