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	$160.92	7.307%	$172.6784	$172.68	$172.70	$172.70
Purchase #2	$157.80	9.367%	$172.5811	$172.58	$172.60	$172.60
Purchase #3	$66.30	5.502%	$69.9478	$69.95	$69.95	$69.90
Purchase #4	$150.35	9.394%	$164.4739	$164.47	$164.45	$164.50
Purchase #5	$152.75	12.740%	$172.2104	$172.21	$172.20	$172.20
Purchase #6	$8.85	3.491%	$9.159	$9.16	$9.15	$9.20
Purchase #7	$105.33	5.603%	$111.2316	$111.23	$111.25	$111.20
7 purchase totals =	$802.30		$872.2822	$872.28	$872.30	$872.30