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	$176.64	7.334%	$189.5948	$189.59	$189.60	$189.60
Purchase #2	$19.46	4.167%	$20.2709	$20.27	$20.25	$20.30
Purchase #3	$209.71	3.734%	$217.5406	$217.54	$217.55	$217.50
Purchase #4	$217.62	7.545%	$234.0394	$234.04	$234.05	$234.00
Purchase #5	$57.40	9.663%	$62.9466	$62.95	$62.95	$62.90
Purchase #6	$34.27	9.587%	$37.5555	$37.56	$37.55	$37.60
Purchase #7	$228.83	13.820%	$260.4543	$260.45	$260.45	$260.50
7 purchase totals =	$943.93		$1,022.4021	$1,022.40	$1,022.40	$1,022.40