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	$132.68	8.168%	$143.5173	$143.52	$143.50	$143.50
Purchase #2	$62.82	7.458%	$67.5051	$67.51	$67.50	$67.50
Purchase #3	$25.85	6.682%	$27.5773	$27.58	$27.60	$27.60
Purchase #4	$136.85	11.833%	$153.0435	$153.04	$153.05	$153.00
Purchase #5	$223.88	4.277%	$233.4553	$233.46	$233.45	$233.50
Purchase #6	$163.76	12.688%	$184.5379	$184.54	$184.55	$184.50
Purchase #7	$207.69	12.712%	$234.0916	$234.09	$234.10	$234.10
7 purchase totals =	$953.53		$1,043.7280	$1,043.74	$1,043.75	$1,043.70