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	$56.68	10.475%	$62.6172	$62.62	$62.60	$62.60
Purchase #2	$143.44	13.352%	$162.5921	$162.59	$162.60	$162.60
Purchase #3	$228.89	4.495%	$239.1786	$239.18	$239.20	$239.20
Purchase #4	$90.81	12.600%	$102.2521	$102.25	$102.25	$102.30
Purchase #5	$75.62	13.570%	$85.8816	$85.88	$85.90	$85.90
Purchase #6	$94.67	9.788%	$103.9363	$103.94	$103.95	$103.90
Purchase #7	$195.29	11.368%	$217.4906	$217.49	$217.50	$217.50
7 purchase totals =	$885.40		$973.9485	$973.95	$974.00	$974.00