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	$127.97	10.440%	$141.3301	$141.33	$141.35	$141.30
Purchase #2	$36.89	6.619%	$39.3317	$39.33	$39.35	$39.30
Purchase #3	$111.98	6.791%	$119.5846	$119.58	$119.60	$119.60
Purchase #4	$199.52	10.697%	$220.8627	$220.86	$220.85	$220.90
Purchase #5	$103.40	10.640%	$114.4018	$114.40	$114.40	$114.40
Purchase #6	$110.25	4.214%	$114.8959	$114.90	$114.90	$114.90
Purchase #7	$100.34	7.660%	$108.026	$108.03	$108.05	$108.00
7 purchase totals =	$790.35		$858.4328	$858.43	$858.50	$858.40