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	$95.25	5.395%	$100.3887	$100.39	$100.40	$100.40
Purchase #2	$81.26	11.810%	$90.8568	$90.86	$90.85	$90.90
Purchase #3	$41.96	9.533%	$45.96	$45.96	$45.95	$46.00
Purchase #4	$20.63	13.336%	$23.3812	$23.38	$23.40	$23.40
Purchase #5	$200.63	8.623%	$217.9303	$217.93	$217.95	$217.90
Purchase #6	$249.47	13.424%	$282.9589	$282.96	$282.95	$283.00
Purchase #7	$172.70	4.152%	$179.8705	$179.87	$179.85	$179.90
7 purchase totals =	$861.90		$941.3464	$941.35	$941.35	$941.50