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	$15.48	7.623%	$16.66	$16.66	$16.65	$16.70
Purchase #2	$91.72	9.238%	$100.1931	$100.19	$100.20	$100.20
Purchase #3	$113.94	6.599%	$121.4589	$121.46	$121.45	$121.50
Purchase #4	$77.36	6.127%	$82.0998	$82.10	$82.10	$82.10
Purchase #5	$114.70	11.241%	$127.5934	$127.59	$127.60	$127.60
Purchase #6	$155.42	3.293%	$160.538	$160.54	$160.55	$160.50
Purchase #7	$81.60	10.304%	$90.0081	$90.01	$90.00	$90.00
7 purchase totals =	$650.22		$698.5513	$698.55	$698.55	$698.60