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	$52.78	6.602%	$56.2645	$56.26	$56.25	$56.30
Purchase #2	$79.45	10.336%	$87.662	$87.66	$87.65	$87.70
Purchase #3	$213.66	4.602%	$223.4926	$223.49	$223.50	$223.50
Purchase #4	$54.48	9.209%	$59.4971	$59.50	$59.50	$59.50
Purchase #5	$56.93	9.596%	$62.393	$62.39	$62.40	$62.40
Purchase #6	$54.69	9.290%	$59.7707	$59.77	$59.75	$59.80
Purchase #7	$196.85	5.531%	$207.7378	$207.74	$207.75	$207.70
7 purchase totals =	$708.84		$756.8177	$756.81	$756.80	$756.90