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	$139.27	7.471%	$149.6749	$149.67	$149.65	$149.70
Purchase #2	$5.90	5.630%	$6.2322	$6.23	$6.25	$6.20
Purchase #3	$40.34	6.692%	$43.0396	$43.04	$43.05	$43.00
Purchase #4	$90.92	10.768%	$100.7103	$100.71	$100.70	$100.70
Purchase #5	$123.80	10.644%	$136.9773	$136.98	$137.00	$137.00
Purchase #6	$176.90	7.504%	$190.1746	$190.17	$190.15	$190.20
Purchase #7	$131.78	9.488%	$144.2833	$144.28	$144.30	$144.30
7 purchase totals =	$708.91		$771.0922	$771.08	$771.10	$771.10