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	$133.58	7.347%	$143.3941	$143.39	$143.40	$143.40
Purchase #2	$20.40	7.634%	$21.9573	$21.96	$21.95	$22.00
Purchase #3	$95.63	4.314%	$99.7555	$99.76	$99.75	$99.80
Purchase #4	$150.43	11.549%	$167.8032	$167.80	$167.80	$167.80
Purchase #5	$9.82	6.874%	$10.495	$10.50	$10.50	$10.50
Purchase #6	$175.60	4.506%	$183.5125	$183.51	$183.50	$183.50
Purchase #7	$168.66	4.710%	$176.6039	$176.60	$176.60	$176.60
7 purchase totals =	$754.12		$803.5215	$803.52	$803.50	$803.60