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	$97.40	3.452%	$100.7622	$100.76	$100.75	$100.80
Purchase #2	$20.31	5.802%	$21.4884	$21.49	$21.50	$21.50
Purchase #3	$10.94	9.662%	$11.997	$12.00	$12.00	$12.00
Purchase #4	$178.66	9.686%	$195.965	$195.97	$195.95	$196.00
Purchase #5	$160.82	13.437%	$182.4294	$182.43	$182.45	$182.40
Purchase #6	$150.27	9.177%	$164.0603	$164.06	$164.05	$164.10
Purchase #7	$89.80	11.838%	$100.4305	$100.43	$100.45	$100.40
7 purchase totals =	$708.20		$777.1328	$777.14	$777.15	$777.20