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	$237.59	9.816%	$260.9118	$260.91	$260.90	$260.90
Purchase #2	$171.88	7.210%	$184.2725	$184.27	$184.25	$184.30
Purchase #3	$127.92	12.470%	$143.8716	$143.87	$143.85	$143.90
Purchase #4	$88.38	6.401%	$94.0372	$94.04	$94.05	$94.00
Purchase #5	$76.41	5.342%	$80.4918	$80.49	$80.50	$80.50
Purchase #6	$126.98	7.359%	$136.3245	$136.32	$136.30	$136.30
Purchase #7	$117.88	5.593%	$124.473	$124.47	$124.45	$124.50
7 purchase totals =	$947.04		$1,024.3824	$1,024.37	$1,024.30	$1,024.40