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	$78.59	11.387%	$87.539	$87.54	$87.55	$87.50
Purchase #2	$160.88	8.164%	$174.0142	$174.01	$174.00	$174.00
Purchase #3	$48.29	6.652%	$51.5023	$51.50	$51.50	$51.50
Purchase #4	$45.99	5.858%	$48.6841	$48.68	$48.70	$48.70
Purchase #5	$69.27	3.653%	$71.8004	$71.80	$71.80	$71.80
Purchase #6	$152.51	12.382%	$171.3938	$171.39	$171.40	$171.40
Purchase #7	$63.81	12.678%	$71.8998	$71.90	$71.90	$71.90
7 purchase totals =	$619.34		$676.8336	$676.82	$676.85	$676.80