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	$137.86	4.396%	$143.9203	$143.92	$143.90	$143.90
Purchase #2	$33.29	11.270%	$37.0418	$37.04	$37.05	$37.00
Purchase #3	$132.63	5.315%	$139.6793	$139.68	$139.70	$139.70
Purchase #4	$133.79	4.348%	$139.6072	$139.61	$139.60	$139.60
Purchase #5	$109.78	9.644%	$120.3672	$120.37	$120.35	$120.40
Purchase #6	$190.73	7.800%	$205.6069	$205.61	$205.60	$205.60
Purchase #7	$246.35	8.849%	$268.1495	$268.15	$268.15	$268.10
7 purchase totals =	$984.43		$1,054.3722	$1,054.38	$1,054.35	$1,054.30