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	$60.75	10.220%	$66.9587	$66.96	$66.95	$67.00
Purchase #2	$166.52	12.307%	$187.0136	$187.01	$187.00	$187.00
Purchase #3	$48.32	6.677%	$51.5463	$51.55	$51.55	$51.50
Purchase #4	$80.90	10.594%	$89.4705	$89.47	$89.45	$89.50
Purchase #5	$208.90	8.418%	$226.4852	$226.49	$226.50	$226.50
Purchase #6	$64.58	13.726%	$73.4443	$73.44	$73.45	$73.40
Purchase #7	$112.75	12.767%	$127.1448	$127.14	$127.15	$127.10
7 purchase totals =	$742.72		$822.0634	$822.06	$822.05	$822.00