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	$214.28	10.817%	$237.4587	$237.46	$237.45	$237.50
Purchase #2	$137.45	10.786%	$152.2754	$152.28	$152.30	$152.30
Purchase #3	$182.92	7.219%	$196.125	$196.13	$196.15	$196.10
Purchase #4	$45.94	11.347%	$51.1528	$51.15	$51.15	$51.20
Purchase #5	$26.79	13.108%	$30.3016	$30.30	$30.30	$30.30
Purchase #6	$70.58	3.182%	$72.8259	$72.83	$72.85	$72.80
Purchase #7	$237.29	8.509%	$257.481	$257.48	$257.50	$257.50
7 purchase totals =	$915.25		$997.6204	$997.63	$997.70	$997.70