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	$181.38	8.173%	$196.2042	$196.20	$196.20	$196.20
Purchase #2	$38.74	10.510%	$42.8116	$42.81	$42.80	$42.80
Purchase #3	$141.49	9.475%	$154.8962	$154.90	$154.90	$154.90
Purchase #4	$107.78	9.545%	$118.0676	$118.07	$118.05	$118.10
Purchase #5	$97.25	8.425%	$105.4433	$105.44	$105.45	$105.40
Purchase #6	$116.71	12.748%	$131.5882	$131.59	$131.60	$131.60
Purchase #7	$225.46	13.454%	$255.7934	$255.79	$255.80	$255.80
7 purchase totals =	$908.81		$1,004.8045	$1,004.80	$1,004.80	$1,004.80