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	$123.89	3.599%	$128.3488	$128.35	$128.35	$128.30
Purchase #2	$12.59	6.186%	$13.3688	$13.37	$13.35	$13.40
Purchase #3	$164.40	4.824%	$172.3307	$172.33	$172.35	$172.30
Purchase #4	$224.75	13.670%	$255.4733	$255.47	$255.45	$255.50
Purchase #5	$191.92	9.382%	$209.9259	$209.93	$209.95	$209.90
Purchase #6	$82.69	3.705%	$85.7537	$85.75	$85.75	$85.80
Purchase #7	$20.63	4.121%	$21.4802	$21.48	$21.50	$21.50
7 purchase totals =	$820.87		$886.6814	$886.68	$886.70	$886.70