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	$175.50	9.660%	$192.4533	$192.45	$192.45	$192.50
Purchase #2	$64.78	3.513%	$67.0557	$67.06	$67.05	$67.10
Purchase #3	$85.66	10.692%	$94.8188	$94.82	$94.80	$94.80
Purchase #4	$33.39	6.566%	$35.5824	$35.58	$35.60	$35.60
Purchase #5	$196.43	3.693%	$203.6842	$203.68	$203.70	$203.70
Purchase #6	$91.49	12.680%	$103.0909	$103.09	$103.10	$103.10
Purchase #7	$220.85	10.262%	$243.5136	$243.51	$243.50	$243.50
7 purchase totals =	$868.10		$940.1989	$940.19	$940.20	$940.30