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	$128.43	4.702%	$134.4688	$134.47	$134.45	$134.50
Purchase #2	$247.66	13.149%	$280.2248	$280.22	$280.20	$280.20
Purchase #3	$123.42	6.555%	$131.5102	$131.51	$131.50	$131.50
Purchase #4	$205.76	4.438%	$214.8916	$214.89	$214.90	$214.90
Purchase #5	$100.79	12.687%	$113.5772	$113.58	$113.60	$113.60
Purchase #6	$119.32	7.285%	$128.0125	$128.01	$128.00	$128.00
Purchase #7	$146.28	6.417%	$155.6668	$155.67	$155.65	$155.70
7 purchase totals =	$1,071.66		$1,158.3519	$1,158.35	$1,158.30	$1,158.40