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	$176.56	13.521%	$200.4327	$200.43	$200.45	$200.40
Purchase #2	$42.26	8.716%	$45.9434	$45.94	$45.95	$45.90
Purchase #3	$175.45	9.730%	$192.5213	$192.52	$192.50	$192.50
Purchase #4	$153.97	13.788%	$175.1994	$175.20	$175.20	$175.20
Purchase #5	$169.37	6.570%	$180.4976	$180.50	$180.50	$180.50
Purchase #6	$94.40	10.822%	$104.616	$104.62	$104.60	$104.60
Purchase #7	$238.37	6.857%	$254.715	$254.72	$254.70	$254.70
7 purchase totals =	$1,050.38		$1,153.9254	$1,153.93	$1,153.90	$1,153.80