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	$209.77	8.109%	$226.7802	$226.78	$226.80	$226.80
Purchase #2	$11.87	4.742%	$12.4329	$12.43	$12.45	$12.40
Purchase #3	$128.48	8.470%	$139.3623	$139.36	$139.35	$139.40
Purchase #4	$157.35	8.682%	$171.0111	$171.01	$171.00	$171.00
Purchase #5	$78.74	8.448%	$85.392	$85.39	$85.40	$85.40
Purchase #6	$132.51	3.512%	$137.1638	$137.16	$137.15	$137.20
Purchase #7	$59.48	5.106%	$62.517	$62.52	$62.50	$62.50
7 purchase totals =	$778.20		$834.6593	$834.65	$834.65	$834.70