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	$189.93	8.466%	$206.0095	$206.01	$206.00	$206.00
Purchase #2	$92.35	8.868%	$100.5396	$100.54	$100.55	$100.50
Purchase #3	$9.64	3.447%	$9.9723	$9.97	$9.95	$10.00
Purchase #4	$40.71	11.262%	$45.2948	$45.29	$45.30	$45.30
Purchase #5	$24.96	10.154%	$27.4944	$27.49	$27.50	$27.50
Purchase #6	$43.88	9.416%	$48.0117	$48.01	$48.00	$48.00
Purchase #7	$54.73	12.567%	$61.6079	$61.61	$61.60	$61.60
7 purchase totals =	$456.20		$498.9302	$498.92	$498.90	$498.90