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	$138.51	10.178%	$152.6075	$152.61	$152.60	$152.60
Purchase #2	$229.79	11.818%	$256.9466	$256.95	$256.95	$256.90
Purchase #3	$147.25	7.861%	$158.8253	$158.83	$158.85	$158.80
Purchase #4	$91.82	9.332%	$100.3886	$100.39	$100.40	$100.40
Purchase #5	$40.46	7.580%	$43.5269	$43.53	$43.55	$43.50
Purchase #6	$96.55	4.705%	$101.0927	$101.09	$101.10	$101.10
Purchase #7	$145.52	3.709%	$150.9173	$150.92	$150.90	$150.90
7 purchase totals =	$889.90		$964.3049	$964.32	$964.35	$964.20