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	$205.45	10.646%	$227.3222	$227.32	$227.30	$227.30
Purchase #2	$38.69	3.156%	$39.9111	$39.91	$39.90	$39.90
Purchase #3	$86.80	10.575%	$95.9791	$95.98	$96.00	$96.00
Purchase #4	$85.48	3.103%	$88.1324	$88.13	$88.15	$88.10
Purchase #5	$94.81	8.450%	$102.8214	$102.82	$102.80	$102.80
Purchase #6	$143.59	9.114%	$156.6768	$156.68	$156.70	$156.70
Purchase #7	$12.82	5.396%	$13.5118	$13.51	$13.50	$13.50
7 purchase totals =	$667.64		$724.3548	$724.35	$724.35	$724.30