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	$20.34	4.838%	$21.324	$21.32	$21.30	$21.30
Purchase #2	$142.80	4.730%	$149.5544	$149.55	$149.55	$149.60
Purchase #3	$155.38	5.180%	$163.4287	$163.43	$163.45	$163.40
Purchase #4	$78.41	10.859%	$86.9245	$86.92	$86.90	$86.90
Purchase #5	$171.51	7.742%	$184.7883	$184.79	$184.80	$184.80
Purchase #6	$177.48	4.493%	$185.4542	$185.45	$185.45	$185.50
Purchase #7	$213.67	6.572%	$227.7124	$227.71	$227.70	$227.70
7 purchase totals =	$959.59		$1,019.1865	$1,019.17	$1,019.15	$1,019.20