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	$228.42	4.455%	$238.5961	$238.60	$238.60	$238.60
Purchase #2	$68.89	13.262%	$78.0262	$78.03	$78.05	$78.00
Purchase #3	$245.98	13.186%	$278.4149	$278.41	$278.40	$278.40
Purchase #4	$92.70	3.564%	$96.0038	$96.00	$96.00	$96.00
Purchase #5	$143.49	7.272%	$153.9246	$153.92	$153.90	$153.90
Purchase #6	$107.71	4.382%	$112.4299	$112.43	$112.45	$112.40
Purchase #7	$69.37	10.453%	$76.6212	$76.62	$76.60	$76.60
7 purchase totals =	$956.56		$1,034.0167	$1,034.01	$1,034.00	$1,033.90