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	$151.49	3.647%	$157.0148	$157.01	$157.00	$157.00
Purchase #2	$224.96	5.826%	$238.0662	$238.07	$238.05	$238.10
Purchase #3	$100.58	12.865%	$113.5196	$113.52	$113.50	$113.50
Purchase #4	$191.90	13.798%	$218.3784	$218.38	$218.40	$218.40
Purchase #5	$144.84	13.360%	$164.1906	$164.19	$164.20	$164.20
Purchase #6	$40.38	12.358%	$45.3702	$45.37	$45.35	$45.40
Purchase #7	$113.49	12.863%	$128.0882	$128.09	$128.10	$128.10
7 purchase totals =	$967.64		$1,064.6280	$1,064.63	$1,064.60	$1,064.70