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	$96.87	8.780%	$105.3752	$105.38	$105.40	$105.40
Purchase #2	$82.43	11.127%	$91.602	$91.60	$91.60	$91.60
Purchase #3	$208.38	11.624%	$232.6021	$232.60	$232.60	$232.60
Purchase #4	$246.86	13.584%	$280.3935	$280.39	$280.40	$280.40
Purchase #5	$192.68	6.731%	$205.6493	$205.65	$205.65	$205.60
Purchase #6	$44.72	7.188%	$47.9345	$47.93	$47.95	$47.90
Purchase #7	$212.62	9.659%	$233.157	$233.16	$233.15	$233.20
7 purchase totals =	$1,084.56		$1,196.7136	$1,196.71	$1,196.75	$1,196.70