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	$174.55	12.490%	$196.3513	$196.35	$196.35	$196.40
Purchase #2	$200.25	8.407%	$217.085	$217.09	$217.10	$217.10
Purchase #3	$102.97	6.794%	$109.9658	$109.97	$109.95	$110.00
Purchase #4	$91.34	10.254%	$100.706	$100.71	$100.70	$100.70
Purchase #5	$101.50	10.433%	$112.0895	$112.09	$112.10	$112.10
Purchase #6	$166.98	5.752%	$176.5847	$176.58	$176.60	$176.60
Purchase #7	$136.56	5.558%	$144.15	$144.15	$144.15	$144.20
7 purchase totals =	$974.15		$1,056.9323	$1,056.94	$1,056.95	$1,057.10