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	$40.69	6.525%	$43.345	$43.35	$43.35	$43.30
Purchase #2	$7.96	12.590%	$8.9622	$8.96	$8.95	$9.00
Purchase #3	$39.78	13.265%	$45.0568	$45.06	$45.05	$45.10
Purchase #4	$160.51	6.801%	$171.4263	$171.43	$171.45	$171.40
Purchase #5	$69.25	7.544%	$74.4742	$74.47	$74.45	$74.50
Purchase #6	$143.88	7.650%	$154.8868	$154.89	$154.90	$154.90
Purchase #7	$105.98	7.631%	$114.0673	$114.07	$114.05	$114.10
7 purchase totals =	$568.05		$612.2186	$612.23	$612.20	$612.30