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	$31.82	10.215%	$35.0704	$35.07	$35.05	$35.10
Purchase #2	$81.45	11.522%	$90.8347	$90.83	$90.85	$90.80
Purchase #3	$19.81	8.812%	$21.5557	$21.56	$21.55	$21.60
Purchase #4	$176.26	4.393%	$184.0031	$184.00	$184.00	$184.00
Purchase #5	$151.35	10.294%	$166.93	$166.93	$166.95	$166.90
Purchase #6	$173.60	3.590%	$179.8322	$179.83	$179.85	$179.80
Purchase #7	$213.55	11.578%	$238.2748	$238.27	$238.25	$238.30
7 purchase totals =	$847.84		$916.5009	$916.49	$916.50	$916.50