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	$56.79	4.455%	$59.32	$59.32	$59.30	$59.30
Purchase #2	$121.32	13.574%	$137.788	$137.79	$137.80	$137.80
Purchase #3	$143.42	9.123%	$156.5042	$156.50	$156.50	$156.50
Purchase #4	$235.49	11.639%	$262.8987	$262.90	$262.90	$262.90
Purchase #5	$205.84	11.340%	$229.1823	$229.18	$229.20	$229.20
Purchase #6	$178.80	6.427%	$190.2915	$190.29	$190.30	$190.30
Purchase #7	$49.51	4.252%	$51.6152	$51.62	$51.60	$51.60
7 purchase totals =	$991.17		$1,087.5999	$1,087.60	$1,087.60	$1,087.60