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	$19.77	3.725%	$20.5064	$20.51	$20.50	$20.50
Purchase #2	$134.51	4.861%	$141.0485	$141.05	$141.05	$141.00
Purchase #3	$145.92	12.526%	$164.1979	$164.20	$164.20	$164.20
Purchase #4	$135.44	11.202%	$150.612	$150.61	$150.60	$150.60
Purchase #5	$114.72	4.288%	$119.6392	$119.64	$119.65	$119.60
Purchase #6	$13.52	10.518%	$14.942	$14.94	$14.95	$14.90
Purchase #7	$136.29	3.507%	$141.0697	$141.07	$141.05	$141.10
7 purchase totals =	$700.17		$752.0157	$752.02	$752.00	$751.90