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	$41.50	4.773%	$43.4808	$43.48	$43.50	$43.50
Purchase #2	$80.43	5.463%	$84.8239	$84.82	$84.80	$84.80
Purchase #3	$153.96	4.311%	$160.5972	$160.60	$160.60	$160.60
Purchase #4	$116.59	12.635%	$131.3211	$131.32	$131.30	$131.30
Purchase #5	$218.82	12.465%	$246.0959	$246.10	$246.10	$246.10
Purchase #6	$43.65	11.268%	$48.5685	$48.57	$48.55	$48.60
Purchase #7	$37.57	8.376%	$40.7169	$40.72	$40.70	$40.70
7 purchase totals =	$692.52		$755.6043	$755.61	$755.55	$755.60