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	$57.78	8.509%	$62.6965	$62.70	$62.70	$62.70
Purchase #2	$94.87	3.585%	$98.2711	$98.27	$98.25	$98.30
Purchase #3	$171.83	3.860%	$178.4626	$178.46	$178.45	$178.50
Purchase #4	$112.98	10.567%	$124.9186	$124.92	$124.90	$124.90
Purchase #5	$199.67	5.693%	$211.0372	$211.04	$211.05	$211.00
Purchase #6	$182.37	7.686%	$196.387	$196.39	$196.40	$196.40
Purchase #7	$11.92	7.303%	$12.7905	$12.79	$12.80	$12.80
7 purchase totals =	$831.42		$884.5635	$884.57	$884.55	$884.60