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	$168.31	4.722%	$176.2576	$176.26	$176.25	$176.30
Purchase #2	$97.98	11.786%	$109.5279	$109.53	$109.55	$109.50
Purchase #3	$36.89	13.484%	$41.8642	$41.86	$41.85	$41.90
Purchase #4	$192.31	12.110%	$215.5987	$215.60	$215.60	$215.60
Purchase #5	$231.27	3.710%	$239.8501	$239.85	$239.85	$239.90
Purchase #6	$40.62	11.594%	$45.3295	$45.33	$45.35	$45.30
Purchase #7	$18.97	3.238%	$19.5842	$19.58	$19.60	$19.60
7 purchase totals =	$786.35		$848.0122	$848.01	$848.05	$848.10