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	$131.41	9.279%	$143.6035	$143.60	$143.60	$143.60
Purchase #2	$192.29	12.273%	$215.8898	$215.89	$215.90	$215.90
Purchase #3	$207.90	5.315%	$218.9499	$218.95	$218.95	$218.90
Purchase #4	$107.36	11.485%	$119.6903	$119.69	$119.70	$119.70
Purchase #5	$131.45	11.429%	$146.4734	$146.47	$146.45	$146.50
Purchase #6	$89.65	5.782%	$94.8336	$94.83	$94.85	$94.80
Purchase #7	$60.50	6.857%	$64.6485	$64.65	$64.65	$64.60
7 purchase totals =	$920.56		$1,004.0890	$1,004.08	$1,004.10	$1,004.00