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	$236.71	9.605%	$259.446	$259.45	$259.45	$259.40
Purchase #2	$164.90	8.483%	$178.8885	$178.89	$178.90	$178.90
Purchase #3	$67.39	8.165%	$72.8924	$72.89	$72.90	$72.90
Purchase #4	$208.37	12.279%	$233.9558	$233.96	$233.95	$234.00
Purchase #5	$154.37	12.749%	$174.0506	$174.05	$174.05	$174.10
Purchase #6	$63.38	13.747%	$72.0928	$72.09	$72.10	$72.10
Purchase #7	$40.97	10.449%	$45.251	$45.25	$45.25	$45.30
7 purchase totals =	$936.09		$1,036.5771	$1,036.58	$1,036.60	$1,036.70