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	$83.27	3.151%	$85.8938	$85.89	$85.90	$85.90
Purchase #2	$51.96	8.774%	$56.519	$56.52	$56.50	$56.50
Purchase #3	$235.46	8.307%	$255.0197	$255.02	$255.00	$255.00
Purchase #4	$48.81	8.247%	$52.8354	$52.84	$52.85	$52.80
Purchase #5	$176.33	11.604%	$196.7913	$196.79	$196.80	$196.80
Purchase #6	$41.98	10.359%	$46.3287	$46.33	$46.35	$46.30
Purchase #7	$105.51	13.454%	$119.7053	$119.71	$119.70	$119.70
7 purchase totals =	$743.32		$813.0932	$813.10	$813.10	$813.00