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	$244.48	4.808%	$256.2346	$256.23	$256.25	$256.20
Purchase #2	$82.83	3.259%	$85.5294	$85.53	$85.55	$85.50
Purchase #3	$108.98	9.464%	$119.2939	$119.29	$119.30	$119.30
Purchase #4	$93.64	11.672%	$104.5697	$104.57	$104.55	$104.60
Purchase #5	$7.93	12.429%	$8.9156	$8.92	$8.90	$8.90
Purchase #6	$133.31	11.468%	$148.598	$148.60	$148.60	$148.60
Purchase #7	$178.91	3.866%	$185.8267	$185.83	$185.85	$185.80
7 purchase totals =	$850.08		$908.9679	$908.97	$909.00	$908.90