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	$13.92	5.244%	$14.65	$14.65	$14.65	$14.70
Purchase #2	$105.61	6.370%	$112.3374	$112.34	$112.35	$112.30
Purchase #3	$87.45	3.863%	$90.8282	$90.83	$90.85	$90.80
Purchase #4	$46.47	11.616%	$51.868	$51.87	$51.85	$51.90
Purchase #5	$249.85	12.494%	$281.0663	$281.07	$281.05	$281.10
Purchase #6	$77.66	13.484%	$88.1317	$88.13	$88.15	$88.10
Purchase #7	$140.51	10.616%	$155.4265	$155.43	$155.45	$155.40
7 purchase totals =	$721.47		$794.3081	$794.32	$794.35	$794.30