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	$29.64	11.593%	$33.0762	$33.08	$33.10	$33.10
Purchase #2	$80.63	4.826%	$84.5212	$84.52	$84.50	$84.50
Purchase #3	$154.29	9.465%	$168.8935	$168.89	$168.90	$168.90
Purchase #4	$197.77	12.510%	$222.511	$222.51	$222.50	$222.50
Purchase #5	$240.90	6.540%	$256.6549	$256.65	$256.65	$256.70
Purchase #6	$202.31	11.610%	$225.7982	$225.80	$225.80	$225.80
Purchase #7	$27.83	11.199%	$30.9467	$30.95	$30.95	$30.90
7 purchase totals =	$933.37		$1,022.4017	$1,022.40	$1,022.40	$1,022.40