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	$242.62	5.414%	$255.7554	$255.76	$255.75	$255.80
Purchase #2	$137.27	11.523%	$153.0876	$153.09	$153.10	$153.10
Purchase #3	$78.32	4.725%	$82.0206	$82.02	$82.00	$82.00
Purchase #4	$172.35	6.833%	$184.1267	$184.13	$184.15	$184.10
Purchase #5	$89.98	13.525%	$102.1498	$102.15	$102.15	$102.10
Purchase #6	$166.25	5.330%	$175.1111	$175.11	$175.10	$175.10
Purchase #7	$79.94	9.250%	$87.3345	$87.33	$87.35	$87.30
7 purchase totals =	$966.73		$1,039.5857	$1,039.59	$1,039.60	$1,039.50