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	$153.45	10.111%	$168.9653	$168.97	$168.95	$169.00
Purchase #2	$132.96	6.737%	$141.9175	$141.92	$141.90	$141.90
Purchase #3	$85.93	12.291%	$96.4917	$96.49	$96.50	$96.50
Purchase #4	$143.28	13.129%	$162.0912	$162.09	$162.10	$162.10
Purchase #5	$189.25	7.150%	$202.7814	$202.78	$202.80	$202.80
Purchase #6	$90.52	5.190%	$95.218	$95.22	$95.20	$95.20
Purchase #7	$149.72	12.513%	$168.4545	$168.45	$168.45	$168.50
7 purchase totals =	$945.11		$1,035.9196	$1,035.92	$1,035.90	$1,036.00