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	$177.93	10.630%	$196.844	$196.84	$196.85	$196.80
Purchase #2	$217.76	4.532%	$227.6289	$227.63	$227.65	$227.60
Purchase #3	$111.66	13.307%	$126.5186	$126.52	$126.50	$126.50
Purchase #4	$127.81	3.297%	$132.0239	$132.02	$132.00	$132.00
Purchase #5	$119.89	11.566%	$133.7565	$133.76	$133.75	$133.80
Purchase #6	$215.98	12.518%	$243.0164	$243.02	$243.00	$243.00
Purchase #7	$49.27	4.797%	$51.6335	$51.63	$51.65	$51.60
7 purchase totals =	$1,020.30		$1,111.4218	$1,111.42	$1,111.40	$1,111.30