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	$119.50	10.127%	$131.6018	$131.60	$131.60	$131.60
Purchase #2	$181.46	5.338%	$191.1463	$191.15	$191.15	$191.10
Purchase #3	$247.49	5.756%	$261.7355	$261.74	$261.75	$261.70
Purchase #4	$107.80	8.379%	$116.8326	$116.83	$116.85	$116.80
Purchase #5	$95.95	9.819%	$105.3713	$105.37	$105.35	$105.40
Purchase #6	$112.61	7.246%	$120.7697	$120.77	$120.75	$120.80
Purchase #7	$97.78	3.258%	$100.9657	$100.97	$100.95	$101.00
7 purchase totals =	$962.59		$1,028.4229	$1,028.43	$1,028.40	$1,028.40