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	$38.32	8.443%	$41.5554	$41.56	$41.55	$41.60
Purchase #2	$132.89	11.300%	$147.9066	$147.91	$147.90	$147.90
Purchase #3	$85.93	5.472%	$90.6321	$90.63	$90.65	$90.60
Purchase #4	$146.68	12.341%	$164.7818	$164.78	$164.80	$164.80
Purchase #5	$100.79	11.566%	$112.4474	$112.45	$112.45	$112.40
Purchase #6	$186.98	11.138%	$207.8058	$207.81	$207.80	$207.80
Purchase #7	$134.63	10.446%	$148.6934	$148.69	$148.70	$148.70
7 purchase totals =	$826.22		$913.8225	$913.83	$913.85	$913.80