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	$50.55	5.584%	$53.3727	$53.37	$53.35	$53.40
Purchase #2	$187.94	3.809%	$195.0986	$195.10	$195.10	$195.10
Purchase #3	$10.46	9.265%	$11.4291	$11.43	$11.45	$11.40
Purchase #4	$44.58	6.223%	$47.3542	$47.35	$47.35	$47.40
Purchase #5	$28.62	9.405%	$31.3117	$31.31	$31.30	$31.30
Purchase #6	$18.94	3.328%	$19.5703	$19.57	$19.55	$19.60
Purchase #7	$176.31	11.234%	$196.1167	$196.12	$196.10	$196.10
7 purchase totals =	$517.40		$554.2533	$554.25	$554.20	$554.30