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	$14.25	8.404%	$15.4476	$15.45	$15.45	$15.40
Purchase #2	$85.98	5.693%	$90.8748	$90.87	$90.85	$90.90
Purchase #3	$186.25	10.459%	$205.7299	$205.73	$205.75	$205.70
Purchase #4	$40.25	13.326%	$45.6137	$45.61	$45.60	$45.60
Purchase #5	$41.36	4.537%	$43.2365	$43.24	$43.25	$43.20
Purchase #6	$234.38	10.228%	$258.3524	$258.35	$258.35	$258.40
Purchase #7	$19.62	5.703%	$20.7389	$20.74	$20.75	$20.70
7 purchase totals =	$622.09		$679.9938	$679.99	$680.00	$679.90