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	$128.85	10.847%	$142.8264	$142.83	$142.85	$142.80
Purchase #2	$148.57	13.475%	$168.5898	$168.59	$168.60	$168.60
Purchase #3	$210.46	8.235%	$227.7914	$227.79	$227.80	$227.80
Purchase #4	$249.57	13.603%	$283.519	$283.52	$283.50	$283.50
Purchase #5	$216.27	10.207%	$238.3447	$238.34	$238.35	$238.30
Purchase #6	$156.49	13.397%	$177.455	$177.46	$177.45	$177.50
Purchase #7	$181.68	3.704%	$188.4094	$188.41	$188.40	$188.40
7 purchase totals =	$1,291.89		$1,426.9357	$1,426.94	$1,426.95	$1,426.90