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	$78.35	9.771%	$86.0056	$86.01	$86.00	$86.00
Purchase #2	$193.42	7.825%	$208.5551	$208.56	$208.55	$208.60
Purchase #3	$185.27	7.208%	$198.6243	$198.62	$198.60	$198.60
Purchase #4	$154.86	9.525%	$169.6104	$169.61	$169.60	$169.60
Purchase #5	$119.30	3.326%	$123.2679	$123.27	$123.25	$123.30
Purchase #6	$76.57	11.485%	$85.3641	$85.36	$85.35	$85.40
Purchase #7	$156.70	4.745%	$164.1354	$164.14	$164.15	$164.10
7 purchase totals =	$964.47		$1,035.5628	$1,035.57	$1,035.50	$1,035.60