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	$116.78	7.825%	$125.918	$125.92	$125.90	$125.90
Purchase #2	$94.31	10.145%	$103.8777	$103.88	$103.90	$103.90
Purchase #3	$62.59	5.347%	$65.9367	$65.94	$65.95	$65.90
Purchase #4	$192.25	9.523%	$210.558	$210.56	$210.55	$210.60
Purchase #5	$163.66	7.305%	$175.6154	$175.62	$175.60	$175.60
Purchase #6	$52.52	5.632%	$55.4779	$55.48	$55.50	$55.50
Purchase #7	$239.96	9.227%	$262.1011	$262.10	$262.10	$262.10
7 purchase totals =	$922.07		$999.4848	$999.50	$999.50	$999.50