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	$9.98	4.570%	$10.4361	$10.44	$10.45	$10.40
Purchase #2	$196.94	10.745%	$218.1012	$218.10	$218.10	$218.10
Purchase #3	$62.91	6.397%	$66.9344	$66.93	$66.95	$66.90
Purchase #4	$112.48	3.683%	$116.6226	$116.62	$116.60	$116.60
Purchase #5	$150.81	10.396%	$166.4882	$166.49	$166.50	$166.50
Purchase #6	$176.98	13.212%	$200.3626	$200.36	$200.35	$200.40
Purchase #7	$108.91	13.361%	$123.4615	$123.46	$123.45	$123.50
7 purchase totals =	$819.01		$902.4066	$902.40	$902.40	$902.40