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	$83.95	5.233%	$88.3431	$88.34	$88.35	$88.30
Purchase #2	$85.34	11.574%	$95.2173	$95.22	$95.20	$95.20
Purchase #3	$10.46	3.739%	$10.8511	$10.85	$10.85	$10.90
Purchase #4	$88.64	10.780%	$98.1954	$98.20	$98.20	$98.20
Purchase #5	$176.37	12.761%	$198.8766	$198.88	$198.90	$198.90
Purchase #6	$47.38	13.724%	$53.8824	$53.88	$53.90	$53.90
Purchase #7	$96.57	8.751%	$105.0208	$105.02	$105.00	$105.00
7 purchase totals =	$588.71		$650.3867	$650.39	$650.40	$650.40