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	$87.74	11.195%	$97.5625	$97.56	$97.55	$97.60
Purchase #2	$250.76	11.693%	$280.0814	$280.08	$280.10	$280.10
Purchase #3	$241.67	8.171%	$261.4169	$261.42	$261.40	$261.40
Purchase #4	$242.30	9.742%	$265.9049	$265.90	$265.90	$265.90
Purchase #5	$169.80	12.416%	$190.8824	$190.88	$190.90	$190.90
Purchase #6	$239.81	4.382%	$250.3185	$250.32	$250.30	$250.30
Purchase #7	$141.33	12.215%	$158.5935	$158.59	$158.60	$158.60
7 purchase totals =	$1,373.41		$1,504.7601	$1,504.75	$1,504.75	$1,504.80