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	$190.80	12.826%	$215.272	$215.27	$215.25	$215.30
Purchase #2	$182.71	3.737%	$189.5379	$189.54	$189.55	$189.50
Purchase #3	$136.88	8.775%	$148.8912	$148.89	$148.90	$148.90
Purchase #4	$50.70	3.270%	$52.3579	$52.36	$52.35	$52.40
Purchase #5	$87.46	10.733%	$96.8471	$96.85	$96.85	$96.80
Purchase #6	$164.60	7.500%	$176.945	$176.95	$176.95	$176.90
Purchase #7	$203.65	7.340%	$218.5979	$218.60	$218.60	$218.60
7 purchase totals =	$1,016.80		$1,098.4490	$1,098.46	$1,098.45	$1,098.40