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	$66.67	6.636%	$71.0942	$71.09	$71.10	$71.10
Purchase #2	$191.61	7.455%	$205.8945	$205.89	$205.90	$205.90
Purchase #3	$191.71	9.646%	$210.2023	$210.20	$210.20	$210.20
Purchase #4	$217.34	7.567%	$233.7861	$233.79	$233.80	$233.80
Purchase #5	$73.88	3.661%	$76.5847	$76.58	$76.60	$76.60
Purchase #6	$131.92	5.821%	$139.5991	$139.60	$139.60	$139.60
Purchase #7	$68.82	5.135%	$72.3539	$72.35	$72.35	$72.40
7 purchase totals =	$941.95		$1,009.5148	$1,009.50	$1,009.55	$1,009.60