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	$238.88	6.768%	$255.0474	$255.05	$255.05	$255.00
Purchase #2	$196.69	10.324%	$216.9963	$217.00	$217.00	$217.00
Purchase #3	$57.89	8.606%	$62.872	$62.87	$62.85	$62.90
Purchase #4	$165.94	13.163%	$187.7827	$187.78	$187.80	$187.80
Purchase #5	$237.32	11.702%	$265.0912	$265.09	$265.10	$265.10
Purchase #6	$160.75	5.849%	$170.1523	$170.15	$170.15	$170.20
Purchase #7	$44.43	3.231%	$45.8655	$45.87	$45.85	$45.90
7 purchase totals =	$1,101.90		$1,203.8074	$1,203.81	$1,203.80	$1,203.90