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	$73.71	10.682%	$81.5837	$81.58	$81.60	$81.60
Purchase #2	$97.30	3.776%	$100.974	$100.97	$100.95	$101.00
Purchase #3	$125.79	11.691%	$140.4961	$140.50	$140.50	$140.50
Purchase #4	$242.82	11.642%	$271.0891	$271.09	$271.10	$271.10
Purchase #5	$157.82	4.241%	$164.5131	$164.51	$164.50	$164.50
Purchase #6	$168.98	13.813%	$192.3212	$192.32	$192.30	$192.30
Purchase #7	$144.68	5.137%	$152.1122	$152.11	$152.10	$152.10
7 purchase totals =	$1,011.10		$1,103.0894	$1,103.08	$1,103.05	$1,103.10