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	$240.27	8.212%	$260.001	$260.00	$260.00	$260.00
Purchase #2	$95.92	6.229%	$101.8949	$101.89	$101.90	$101.90
Purchase #3	$119.60	3.108%	$123.3172	$123.32	$123.30	$123.30
Purchase #4	$11.94	7.400%	$12.8236	$12.82	$12.80	$12.80
Purchase #5	$172.95	7.277%	$185.5356	$185.54	$185.55	$185.50
Purchase #6	$37.75	3.851%	$39.2038	$39.20	$39.20	$39.20
Purchase #7	$132.89	7.843%	$143.3126	$143.31	$143.30	$143.30
7 purchase totals =	$811.32		$866.0887	$866.08	$866.05	$866.00