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	$89.52	6.654%	$95.4767	$95.48	$95.50	$95.50
Purchase #2	$89.40	9.546%	$97.9341	$97.93	$97.95	$97.90
Purchase #3	$207.72	6.124%	$220.4408	$220.44	$220.45	$220.40
Purchase #4	$81.45	11.221%	$90.5895	$90.59	$90.60	$90.60
Purchase #5	$215.25	4.660%	$225.2807	$225.28	$225.30	$225.30
Purchase #6	$154.98	7.572%	$166.7151	$166.72	$166.70	$166.70
Purchase #7	$71.68	6.768%	$76.5313	$76.53	$76.55	$76.50
7 purchase totals =	$910.00		$972.9682	$972.97	$973.05	$972.90