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	$78.46	6.325%	$83.4226	$83.42	$83.40	$83.40
Purchase #2	$168.46	3.339%	$174.0849	$174.08	$174.10	$174.10
Purchase #3	$67.82	11.724%	$75.7712	$75.77	$75.75	$75.80
Purchase #4	$136.63	3.873%	$141.9217	$141.92	$141.90	$141.90
Purchase #5	$131.60	12.134%	$147.5683	$147.57	$147.55	$147.60
Purchase #6	$189.84	3.695%	$196.8546	$196.85	$196.85	$196.90
Purchase #7	$100.48	13.342%	$113.886	$113.89	$113.90	$113.90
7 purchase totals =	$873.29		$933.5093	$933.50	$933.45	$933.60