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	$92.43	13.215%	$104.6446	$104.64	$104.65	$104.60
Purchase #2	$62.66	6.639%	$66.82	$66.82	$66.80	$66.80
Purchase #3	$67.56	4.663%	$70.7103	$70.71	$70.70	$70.70
Purchase #4	$11.78	13.616%	$13.384	$13.38	$13.40	$13.40
Purchase #5	$13.70	3.240%	$14.1439	$14.14	$14.15	$14.10
Purchase #6	$156.63	13.372%	$177.5746	$177.57	$177.55	$177.60
Purchase #7	$63.64	13.772%	$72.4045	$72.40	$72.40	$72.40
7 purchase totals =	$468.40		$519.6819	$519.66	$519.65	$519.60