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	$71.52	12.712%	$80.6116	$80.61	$80.60	$80.60
Purchase #2	$143.87	11.196%	$159.9777	$159.98	$160.00	$160.00
Purchase #3	$145.95	3.410%	$150.9269	$150.93	$150.95	$150.90
Purchase #4	$157.95	9.489%	$172.9379	$172.94	$172.95	$172.90
Purchase #5	$175.90	3.261%	$181.6361	$181.64	$181.65	$181.60
Purchase #6	$92.78	12.619%	$104.4879	$104.49	$104.50	$104.50
Purchase #7	$173.95	10.673%	$192.5157	$192.52	$192.50	$192.50
7 purchase totals =	$961.92		$1,043.0938	$1,043.11	$1,043.15	$1,043.00