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	$128.42	7.217%	$137.6881	$137.69	$137.70	$137.70
Purchase #2	$63.44	13.710%	$72.1376	$72.14	$72.15	$72.10
Purchase #3	$105.42	7.555%	$113.3845	$113.38	$113.40	$113.40
Purchase #4	$237.42	10.382%	$262.0689	$262.07	$262.05	$262.10
Purchase #5	$127.39	11.405%	$141.9188	$141.92	$141.90	$141.90
Purchase #6	$148.94	6.594%	$158.7611	$158.76	$158.75	$158.80
Purchase #7	$15.50	6.450%	$16.4998	$16.50	$16.50	$16.50
7 purchase totals =	$826.53		$902.4588	$902.46	$902.45	$902.50