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	$217.87	7.182%	$233.5174	$233.52	$233.50	$233.50
Purchase #2	$42.96	11.326%	$47.8256	$47.83	$47.85	$47.80
Purchase #3	$196.77	7.475%	$211.4786	$211.48	$211.50	$211.50
Purchase #4	$29.71	7.616%	$31.9727	$31.97	$31.95	$32.00
Purchase #5	$216.59	8.751%	$235.5438	$235.54	$235.55	$235.50
Purchase #6	$111.50	4.617%	$116.648	$116.65	$116.65	$116.60
Purchase #7	$7.29	6.466%	$7.7614	$7.76	$7.75	$7.80
7 purchase totals =	$822.69		$884.7475	$884.75	$884.75	$884.70