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	$208.75	3.419%	$215.8872	$215.89	$215.90	$215.90
Purchase #2	$157.37	8.785%	$171.195	$171.20	$171.20	$171.20
Purchase #3	$238.76	8.421%	$258.866	$258.87	$258.85	$258.90
Purchase #4	$17.78	9.167%	$19.4099	$19.41	$19.40	$19.40
Purchase #5	$234.89	9.360%	$256.8757	$256.88	$256.90	$256.90
Purchase #6	$18.75	7.116%	$20.0843	$20.08	$20.10	$20.10
Purchase #7	$177.79	12.266%	$199.5977	$199.60	$199.60	$199.60
7 purchase totals =	$1,054.09		$1,141.9158	$1,141.93	$1,141.95	$1,142.00