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	$77.79	9.342%	$85.0571	$85.06	$85.05	$85.10
Purchase #2	$182.98	5.387%	$192.8371	$192.84	$192.85	$192.80
Purchase #3	$211.77	5.117%	$222.6063	$222.61	$222.60	$222.60
Purchase #4	$77.26	7.526%	$83.0746	$83.07	$83.05	$83.10
Purchase #5	$217.71	10.558%	$240.6958	$240.70	$240.70	$240.70
Purchase #6	$194.47	9.178%	$212.3185	$212.32	$212.30	$212.30
Purchase #7	$17.89	13.871%	$20.3715	$20.37	$20.35	$20.40
7 purchase totals =	$979.87		$1,056.9609	$1,056.97	$1,056.90	$1,057.00