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	$215.39	9.692%	$236.2656	$236.27	$236.25	$236.30
Purchase #2	$123.29	7.281%	$132.2667	$132.27	$132.25	$132.30
Purchase #3	$162.58	4.513%	$169.9172	$169.92	$169.90	$169.90
Purchase #4	$16.32	10.751%	$18.0746	$18.07	$18.05	$18.10
Purchase #5	$42.93	12.450%	$48.2748	$48.27	$48.25	$48.30
Purchase #6	$249.60	7.145%	$267.4339	$267.43	$267.45	$267.40
Purchase #7	$182.79	7.278%	$196.0935	$196.09	$196.10	$196.10
7 purchase totals =	$992.90		$1,068.3263	$1,068.32	$1,068.25	$1,068.40