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	$163.38	3.779%	$169.5541	$169.55	$169.55	$169.60
Purchase #2	$228.40	10.837%	$253.1517	$253.15	$253.15	$253.20
Purchase #3	$148.43	10.609%	$164.1769	$164.18	$164.20	$164.20
Purchase #4	$43.69	5.108%	$45.9217	$45.92	$45.90	$45.90
Purchase #5	$144.51	4.186%	$150.5592	$150.56	$150.55	$150.60
Purchase #6	$94.45	8.409%	$102.3923	$102.39	$102.40	$102.40
Purchase #7	$74.57	5.255%	$78.4887	$78.49	$78.50	$78.50
7 purchase totals =	$897.43		$964.2446	$964.24	$964.25	$964.40