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	$250.45	6.822%	$267.5357	$267.54	$267.55	$267.50
Purchase #2	$217.94	6.442%	$231.9797	$231.98	$232.00	$232.00
Purchase #3	$164.28	5.572%	$173.4337	$173.43	$173.45	$173.40
Purchase #4	$75.43	10.206%	$83.1284	$83.13	$83.15	$83.10
Purchase #5	$101.88	7.565%	$109.5872	$109.59	$109.60	$109.60
Purchase #6	$41.52	8.555%	$45.072	$45.07	$45.05	$45.10
Purchase #7	$16.85	13.671%	$19.1536	$19.15	$19.15	$19.20
7 purchase totals =	$868.35		$929.8903	$929.89	$929.95	$929.90