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	$66.29	8.109%	$71.6655	$71.67	$71.65	$71.70
Purchase #2	$208.69	9.185%	$227.8582	$227.86	$227.85	$227.90
Purchase #3	$16.33	8.829%	$17.7718	$17.77	$17.75	$17.80
Purchase #4	$45.54	10.185%	$50.1782	$50.18	$50.20	$50.20
Purchase #5	$77.63	3.611%	$80.4332	$80.43	$80.45	$80.40
Purchase #6	$41.90	8.507%	$45.4644	$45.46	$45.45	$45.50
Purchase #7	$148.71	6.591%	$158.5115	$158.51	$158.50	$158.50
7 purchase totals =	$605.09		$651.8828	$651.88	$651.85	$652.00