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	$121.69	8.329%	$131.8256	$131.83	$131.85	$131.80
Purchase #2	$117.87	13.166%	$133.3888	$133.39	$133.40	$133.40
Purchase #3	$149.31	10.395%	$164.8308	$164.83	$164.85	$164.80
Purchase #4	$118.83	10.631%	$131.4628	$131.46	$131.45	$131.50
Purchase #5	$116.40	8.705%	$126.5326	$126.53	$126.55	$126.50
Purchase #6	$168.39	8.731%	$183.0921	$183.09	$183.10	$183.10
Purchase #7	$217.82	4.319%	$227.2276	$227.23	$227.25	$227.20
7 purchase totals =	$1,010.31		$1,098.3603	$1,098.36	$1,098.45	$1,098.30