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	$216.89	9.859%	$238.2732	$238.27	$238.25	$238.30
Purchase #2	$78.40	8.161%	$84.7982	$84.80	$84.80	$84.80
Purchase #3	$88.56	8.156%	$95.783	$95.78	$95.80	$95.80
Purchase #4	$100.31	8.286%	$108.6217	$108.62	$108.60	$108.60
Purchase #5	$36.72	12.570%	$41.3357	$41.34	$41.35	$41.30
Purchase #6	$148.86	6.288%	$158.2203	$158.22	$158.20	$158.20
Purchase #7	$143.52	3.500%	$148.5432	$148.54	$148.55	$148.50
7 purchase totals =	$813.26		$875.5753	$875.57	$875.55	$875.50