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	$73.82	3.762%	$76.5971	$76.60	$76.60	$76.60
Purchase #2	$67.78	6.247%	$72.0142	$72.01	$72.00	$72.00
Purchase #3	$199.84	8.661%	$217.1481	$217.15	$217.15	$217.10
Purchase #4	$57.43	3.252%	$59.2976	$59.30	$59.30	$59.30
Purchase #5	$136.63	3.764%	$141.7728	$141.77	$141.75	$141.80
Purchase #6	$226.68	6.714%	$241.8993	$241.90	$241.90	$241.90
Purchase #7	$86.67	10.115%	$95.4367	$95.44	$95.45	$95.40
7 purchase totals =	$848.85		$904.1658	$904.17	$904.15	$904.10