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	$119.46	11.529%	$133.2325	$133.23	$133.25	$133.20
Purchase #2	$131.91	10.566%	$145.8476	$145.85	$145.85	$145.80
Purchase #3	$65.66	5.750%	$69.4355	$69.44	$69.45	$69.40
Purchase #4	$84.58	12.244%	$94.936	$94.94	$94.95	$94.90
Purchase #5	$170.78	6.267%	$181.4828	$181.48	$181.50	$181.50
Purchase #6	$39.43	10.588%	$43.6048	$43.60	$43.60	$43.60
Purchase #7	$78.44	13.687%	$89.1761	$89.18	$89.20	$89.20
7 purchase totals =	$690.26		$757.7153	$757.72	$757.80	$757.60