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	$201.68	5.552%	$212.8773	$212.88	$212.90	$212.90
Purchase #2	$48.38	5.826%	$51.1986	$51.20	$51.20	$51.20
Purchase #3	$41.58	9.558%	$45.5542	$45.55	$45.55	$45.60
Purchase #4	$14.43	13.153%	$16.328	$16.33	$16.35	$16.30
Purchase #5	$169.90	10.381%	$187.5373	$187.54	$187.55	$187.50
Purchase #6	$170.60	12.217%	$191.4422	$191.44	$191.45	$191.40
Purchase #7	$84.88	5.583%	$89.6189	$89.62	$89.60	$89.60
7 purchase totals =	$731.45		$794.5565	$794.56	$794.60	$794.50