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	$27.94	5.185%	$29.3887	$29.39	$29.40	$29.40
Purchase #2	$49.51	4.723%	$51.8484	$51.85	$51.85	$51.80
Purchase #3	$236.90	9.159%	$258.5977	$258.60	$258.60	$258.60
Purchase #4	$21.54	12.145%	$24.156	$24.16	$24.15	$24.20
Purchase #5	$183.67	6.766%	$196.0971	$196.10	$196.10	$196.10
Purchase #6	$138.33	10.329%	$152.6181	$152.62	$152.60	$152.60
Purchase #7	$19.27	6.526%	$20.5276	$20.53	$20.55	$20.50
7 purchase totals =	$677.16		$733.2336	$733.25	$733.25	$733.20