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	$128.34	10.704%	$142.0775	$142.08	$142.10	$142.10
Purchase #2	$156.93	4.792%	$164.4501	$164.45	$164.45	$164.50
Purchase #3	$59.68	4.509%	$62.371	$62.37	$62.35	$62.40
Purchase #4	$50.70	4.709%	$53.0875	$53.09	$53.10	$53.10
Purchase #5	$198.30	11.228%	$220.5651	$220.57	$220.55	$220.60
Purchase #6	$138.43	3.380%	$143.1089	$143.11	$143.10	$143.10
Purchase #7	$89.32	6.473%	$95.1017	$95.10	$95.10	$95.10
7 purchase totals =	$821.70		$880.7618	$880.77	$880.75	$880.90