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	$93.63	12.467%	$105.3029	$105.30	$105.30	$105.30
Purchase #2	$64.49	12.115%	$72.303	$72.30	$72.30	$72.30
Purchase #3	$142.50	8.577%	$154.7222	$154.72	$154.70	$154.70
Purchase #4	$220.93	10.833%	$244.8633	$244.86	$244.85	$244.90
Purchase #5	$48.75	4.678%	$51.0305	$51.03	$51.05	$51.00
Purchase #6	$179.33	7.366%	$192.5394	$192.54	$192.55	$192.50
Purchase #7	$240.55	10.299%	$265.3242	$265.32	$265.30	$265.30
7 purchase totals =	$990.18		$1,086.0855	$1,086.07	$1,086.05	$1,086.00