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	$39.60	4.856%	$41.523	$41.52	$41.50	$41.50
Purchase #2	$127.34	3.707%	$132.0605	$132.06	$132.05	$132.10
Purchase #3	$25.95	10.204%	$28.5979	$28.60	$28.60	$28.60
Purchase #4	$27.82	9.622%	$30.4968	$30.50	$30.50	$30.50
Purchase #5	$237.94	7.186%	$255.0384	$255.04	$255.05	$255.00
Purchase #6	$13.71	6.187%	$14.5582	$14.56	$14.55	$14.60
Purchase #7	$182.36	4.472%	$190.5151	$190.52	$190.50	$190.50
7 purchase totals =	$654.72		$692.7899	$692.80	$692.75	$692.80