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	$241.51	9.806%	$265.1925	$265.19	$265.20	$265.20
Purchase #2	$176.75	9.701%	$193.8965	$193.90	$193.90	$193.90
Purchase #3	$200.52	5.392%	$211.332	$211.33	$211.35	$211.30
Purchase #4	$131.81	4.111%	$137.2287	$137.23	$137.25	$137.20
Purchase #5	$74.38	8.258%	$80.5223	$80.52	$80.50	$80.50
Purchase #6	$102.89	8.379%	$111.5112	$111.51	$111.50	$111.50
Purchase #7	$52.75	13.183%	$59.704	$59.70	$59.70	$59.70
7 purchase totals =	$980.61		$1,059.3872	$1,059.38	$1,059.40	$1,059.30