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	$105.25	9.632%	$115.3877	$115.39	$115.40	$115.40
Purchase #2	$19.83	6.601%	$21.139	$21.14	$21.15	$21.10
Purchase #3	$154.86	11.447%	$172.5868	$172.59	$172.60	$172.60
Purchase #4	$75.85	3.611%	$78.5889	$78.59	$78.60	$78.60
Purchase #5	$51.93	4.689%	$54.365	$54.37	$54.35	$54.40
Purchase #6	$207.46	4.214%	$216.2024	$216.20	$216.20	$216.20
Purchase #7	$114.74	6.190%	$121.8424	$121.84	$121.85	$121.80
7 purchase totals =	$729.92		$780.1122	$780.12	$780.15	$780.10