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	$68.81	4.665%	$72.02	$72.02	$72.00	$72.00
Purchase #2	$121.41	8.635%	$131.8938	$131.89	$131.90	$131.90
Purchase #3	$105.50	6.808%	$112.6824	$112.68	$112.70	$112.70
Purchase #4	$129.29	9.748%	$141.8932	$141.89	$141.90	$141.90
Purchase #5	$247.61	3.134%	$255.3701	$255.37	$255.35	$255.40
Purchase #6	$229.69	12.174%	$257.6525	$257.65	$257.65	$257.70
Purchase #7	$41.54	13.235%	$47.0378	$47.04	$47.05	$47.00
7 purchase totals =	$943.85		$1,018.5498	$1,018.54	$1,018.55	$1,018.60