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	$126.84	10.274%	$139.8715	$139.87	$139.85	$139.90
Purchase #2	$247.82	8.606%	$269.1474	$269.15	$269.15	$269.10
Purchase #3	$196.43	9.718%	$215.5191	$215.52	$215.50	$215.50
Purchase #4	$45.36	8.513%	$49.2215	$49.22	$49.20	$49.20
Purchase #5	$58.89	6.122%	$62.4952	$62.50	$62.50	$62.50
Purchase #6	$222.83	8.433%	$241.6213	$241.62	$241.60	$241.60
Purchase #7	$63.89	8.738%	$69.4727	$69.47	$69.45	$69.50
7 purchase totals =	$962.06		$1,047.3487	$1,047.35	$1,047.25	$1,047.30