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	$82.69	8.343%	$89.5888	$89.59	$89.60	$89.60
Purchase #2	$91.66	10.814%	$101.5721	$101.57	$101.55	$101.60
Purchase #3	$243.96	4.645%	$255.2919	$255.29	$255.30	$255.30
Purchase #4	$154.86	10.729%	$171.4749	$171.47	$171.45	$171.50
Purchase #5	$120.87	10.233%	$133.2386	$133.24	$133.25	$133.20
Purchase #6	$189.52	7.326%	$203.4042	$203.40	$203.40	$203.40
Purchase #7	$12.51	12.273%	$14.0454	$14.05	$14.05	$14.00
7 purchase totals =	$896.07		$968.6159	$968.61	$968.60	$968.60