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	$178.50	6.584%	$190.2524	$190.25	$190.25	$190.30
Purchase #2	$248.82	6.460%	$264.8938	$264.89	$264.90	$264.90
Purchase #3	$171.85	5.866%	$181.9307	$181.93	$181.95	$181.90
Purchase #4	$83.95	4.536%	$87.758	$87.76	$87.75	$87.80
Purchase #5	$118.96	10.868%	$131.8886	$131.89	$131.90	$131.90
Purchase #6	$196.33	8.194%	$212.4173	$212.42	$212.40	$212.40
Purchase #7	$24.70	11.182%	$27.462	$27.46	$27.45	$27.50
7 purchase totals =	$1,023.11		$1,096.6028	$1,096.60	$1,096.60	$1,096.70