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	$220.78	3.581%	$228.6861	$228.69	$228.70	$228.70
Purchase #2	$51.26	9.130%	$55.94	$55.94	$55.95	$55.90
Purchase #3	$56.66	12.847%	$63.9391	$63.94	$63.95	$63.90
Purchase #4	$248.27	12.797%	$280.0411	$280.04	$280.05	$280.00
Purchase #5	$65.42	10.833%	$72.5069	$72.51	$72.50	$72.50
Purchase #6	$180.66	5.510%	$190.6144	$190.61	$190.60	$190.60
Purchase #7	$237.79	11.664%	$265.5258	$265.53	$265.55	$265.50
7 purchase totals =	$1,060.84		$1,157.2534	$1,157.26	$1,157.30	$1,157.10