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	$193.26	3.517%	$200.057	$200.06	$200.05	$200.10
Purchase #2	$105.40	7.105%	$112.8887	$112.89	$112.90	$112.90
Purchase #3	$210.92	4.602%	$220.6265	$220.63	$220.65	$220.60
Purchase #4	$134.78	7.119%	$144.375	$144.38	$144.40	$144.40
Purchase #5	$85.83	13.189%	$97.1501	$97.15	$97.15	$97.20
Purchase #6	$241.55	8.469%	$262.0069	$262.01	$262.00	$262.00
Purchase #7	$42.40	3.647%	$43.9463	$43.95	$43.95	$43.90
7 purchase totals =	$1,014.14		$1,081.0505	$1,081.07	$1,081.10	$1,081.10