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	$209.62	3.797%	$217.5793	$217.58	$217.60	$217.60
Purchase #2	$200.57	13.205%	$227.0553	$227.06	$227.05	$227.10
Purchase #3	$72.93	13.218%	$82.5699	$82.57	$82.55	$82.60
Purchase #4	$84.60	13.442%	$95.9719	$95.97	$95.95	$96.00
Purchase #5	$239.85	9.534%	$262.7173	$262.72	$262.70	$262.70
Purchase #6	$19.27	13.338%	$21.8402	$21.84	$21.85	$21.80
Purchase #7	$103.71	7.219%	$111.1968	$111.20	$111.20	$111.20
7 purchase totals =	$930.55		$1,018.9307	$1,018.94	$1,018.90	$1,019.00