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	$104.79	6.493%	$111.594	$111.59	$111.60	$111.60
Purchase #2	$186.58	11.263%	$207.5945	$207.59	$207.60	$207.60
Purchase #3	$26.67	3.325%	$27.5568	$27.56	$27.55	$27.60
Purchase #4	$240.51	6.418%	$255.9459	$255.95	$255.95	$255.90
Purchase #5	$11.25	11.217%	$12.5119	$12.51	$12.50	$12.50
Purchase #6	$108.54	9.258%	$118.5886	$118.59	$118.60	$118.60
Purchase #7	$249.78	11.379%	$278.2025	$278.20	$278.20	$278.20
7 purchase totals =	$928.12		$1,011.9942	$1,011.99	$1,012.00	$1,012.00