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	$87.29	9.209%	$95.3285	$95.33	$95.35	$95.30
Purchase #2	$50.70	9.305%	$55.4176	$55.42	$55.40	$55.40
Purchase #3	$186.90	11.559%	$208.5038	$208.50	$208.50	$208.50
Purchase #4	$29.50	8.206%	$31.9208	$31.92	$31.90	$31.90
Purchase #5	$124.57	3.499%	$128.9287	$128.93	$128.95	$128.90
Purchase #6	$56.95	4.648%	$59.597	$59.60	$59.60	$59.60
Purchase #7	$217.74	9.429%	$238.2707	$238.27	$238.25	$238.30
7 purchase totals =	$753.65		$817.9671	$817.97	$817.95	$817.90