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	$10.90	4.874%	$11.4313	$11.43	$11.45	$11.40
Purchase #2	$249.51	4.158%	$259.8846	$259.88	$259.90	$259.90
Purchase #3	$212.68	4.211%	$221.636	$221.64	$221.65	$221.60
Purchase #4	$13.36	6.853%	$14.2756	$14.28	$14.30	$14.30
Purchase #5	$112.57	3.131%	$116.0946	$116.09	$116.10	$116.10
Purchase #6	$46.79	10.508%	$51.7067	$51.71	$51.70	$51.70
Purchase #7	$189.97	3.645%	$196.8944	$196.89	$196.90	$196.90
7 purchase totals =	$835.78		$871.9232	$871.92	$872.00	$871.90