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	$12.83	12.593%	$14.4457	$14.45	$14.45	$14.40
Purchase #2	$243.88	5.588%	$257.508	$257.51	$257.50	$257.50
Purchase #3	$101.39	4.147%	$105.5946	$105.59	$105.60	$105.60
Purchase #4	$90.99	11.426%	$101.3865	$101.39	$101.40	$101.40
Purchase #5	$102.36	9.316%	$111.8959	$111.90	$111.90	$111.90
Purchase #6	$100.51	9.296%	$109.8534	$109.85	$109.85	$109.90
Purchase #7	$141.45	11.545%	$157.7804	$157.78	$157.80	$157.80
7 purchase totals =	$793.41		$858.4645	$858.47	$858.50	$858.50