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	$92.79	8.686%	$100.8497	$100.85	$100.85	$100.80
Purchase #2	$167.34	11.636%	$186.8117	$186.81	$186.80	$186.80
Purchase #3	$17.80	11.867%	$19.9123	$19.91	$19.90	$19.90
Purchase #4	$152.50	7.296%	$163.6264	$163.63	$163.65	$163.60
Purchase #5	$228.54	13.718%	$259.8911	$259.89	$259.90	$259.90
Purchase #6	$219.29	10.587%	$242.5062	$242.51	$242.50	$242.50
Purchase #7	$40.43	5.758%	$42.758	$42.76	$42.75	$42.80
7 purchase totals =	$918.69		$1,016.3554	$1,016.36	$1,016.35	$1,016.30