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	$9.70	9.511%	$10.6226	$10.62	$10.60	$10.60
Purchase #2	$206.80	8.266%	$223.8941	$223.89	$223.90	$223.90
Purchase #3	$214.82	7.335%	$230.577	$230.58	$230.60	$230.60
Purchase #4	$14.55	6.569%	$15.5058	$15.51	$15.50	$15.50
Purchase #5	$194.25	7.840%	$209.4792	$209.48	$209.50	$209.50
Purchase #6	$239.43	6.661%	$255.3784	$255.38	$255.40	$255.40
Purchase #7	$102.99	10.592%	$113.8987	$113.90	$113.90	$113.90
7 purchase totals =	$982.54		$1,059.3558	$1,059.36	$1,059.40	$1,059.40