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	$128.45	7.406%	$137.963	$137.96	$137.95	$138.00
Purchase #2	$43.95	3.596%	$45.5304	$45.53	$45.55	$45.50
Purchase #3	$93.75	12.811%	$105.7603	$105.76	$105.75	$105.80
Purchase #4	$109.97	12.483%	$123.6976	$123.70	$123.70	$123.70
Purchase #5	$136.32	5.551%	$143.8871	$143.89	$143.90	$143.90
Purchase #6	$123.75	3.242%	$127.762	$127.76	$127.75	$127.80
Purchase #7	$179.48	11.211%	$199.6015	$199.60	$199.60	$199.60
7 purchase totals =	$815.67		$884.2019	$884.20	$884.20	$884.30