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	$61.40	11.244%	$68.3038	$68.30	$68.30	$68.30
Purchase #2	$40.37	8.574%	$43.8313	$43.83	$43.85	$43.80
Purchase #3	$6.86	5.750%	$7.2545	$7.25	$7.25	$7.30
Purchase #4	$113.95	9.639%	$124.9336	$124.93	$124.95	$124.90
Purchase #5	$227.92	12.529%	$256.4761	$256.48	$256.50	$256.50
Purchase #6	$191.88	4.382%	$200.2882	$200.29	$200.30	$200.30
Purchase #7	$233.88	9.184%	$255.3595	$255.36	$255.35	$255.40
7 purchase totals =	$876.26		$956.4470	$956.44	$956.50	$956.50