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	$53.86	10.865%	$59.7119	$59.71	$59.70	$59.70
Purchase #2	$221.94	8.660%	$241.16	$241.16	$241.15	$241.20
Purchase #3	$102.39	9.483%	$112.0996	$112.10	$112.10	$112.10
Purchase #4	$248.27	5.762%	$262.5753	$262.58	$262.60	$262.60
Purchase #5	$91.71	12.698%	$103.3553	$103.36	$103.35	$103.40
Purchase #6	$17.25	10.132%	$18.9978	$19.00	$19.00	$19.00
Purchase #7	$57.93	5.863%	$61.3264	$61.33	$61.35	$61.30
7 purchase totals =	$793.35		$859.2263	$859.24	$859.25	$859.30