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	$153.84	13.402%	$174.4576	$174.46	$174.45	$174.50
Purchase #2	$142.37	6.210%	$151.2112	$151.21	$151.20	$151.20
Purchase #3	$92.55	7.863%	$99.8272	$99.83	$99.85	$99.80
Purchase #4	$246.75	10.306%	$272.1801	$272.18	$272.20	$272.20
Purchase #5	$100.37	11.450%	$111.8624	$111.86	$111.85	$111.90
Purchase #6	$116.43	4.457%	$121.6193	$121.62	$121.60	$121.60
Purchase #7	$12.64	9.318%	$13.8178	$13.82	$13.80	$13.80
7 purchase totals =	$864.95		$944.9756	$944.98	$944.95	$945.00