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	$119.94	9.605%	$131.4602	$131.46	$131.45	$131.50
Purchase #2	$195.57	8.475%	$212.1446	$212.14	$212.15	$212.10
Purchase #3	$176.49	3.663%	$182.9548	$182.95	$182.95	$183.00
Purchase #4	$29.65	10.705%	$32.824	$32.82	$32.80	$32.80
Purchase #5	$53.97	5.455%	$56.9141	$56.91	$56.90	$56.90
Purchase #6	$87.59	5.523%	$92.4276	$92.43	$92.45	$92.40
Purchase #7	$86.53	3.469%	$89.5317	$89.53	$89.55	$89.50
7 purchase totals =	$749.74		$798.2570	$798.24	$798.25	$798.20