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	$92.28	9.295%	$100.8574	$100.86	$100.85	$100.90
Purchase #2	$176.35	11.333%	$196.3357	$196.34	$196.35	$196.30
Purchase #3	$195.47	11.105%	$217.1769	$217.18	$217.20	$217.20
Purchase #4	$122.30	11.338%	$136.1664	$136.17	$136.15	$136.20
Purchase #5	$19.48	13.563%	$22.1221	$22.12	$22.10	$22.10
Purchase #6	$102.43	13.284%	$116.0368	$116.04	$116.05	$116.00
Purchase #7	$179.51	11.660%	$200.4409	$200.44	$200.45	$200.40
7 purchase totals =	$887.82		$989.1362	$989.15	$989.15	$989.10