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	$96.59	6.439%	$102.8094	$102.81	$102.80	$102.80
Purchase #2	$103.98	7.239%	$111.5071	$111.51	$111.50	$111.50
Purchase #3	$107.75	11.854%	$120.5227	$120.52	$120.50	$120.50
Purchase #4	$89.67	11.325%	$99.8251	$99.83	$99.85	$99.80
Purchase #5	$113.69	4.477%	$118.7799	$118.78	$118.80	$118.80
Purchase #6	$207.94	5.429%	$219.2291	$219.23	$219.25	$219.20
Purchase #7	$217.74	4.828%	$228.2525	$228.25	$228.25	$228.30
7 purchase totals =	$937.36		$1,000.9258	$1,000.93	$1,000.95	$1,000.90