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	$14.82	8.600%	$16.0945	$16.09	$16.10	$16.10
Purchase #2	$90.72	6.425%	$96.5488	$96.55	$96.55	$96.50
Purchase #3	$12.48	13.682%	$14.1875	$14.19	$14.20	$14.20
Purchase #4	$15.66	11.552%	$17.469	$17.47	$17.45	$17.50
Purchase #5	$134.66	7.627%	$144.9305	$144.93	$144.95	$144.90
Purchase #6	$81.51	10.239%	$89.8558	$89.86	$89.85	$89.90
Purchase #7	$57.40	6.385%	$61.065	$61.07	$61.05	$61.10
7 purchase totals =	$407.25		$440.1511	$440.16	$440.15	$440.20