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	$240.67	7.425%	$258.5397	$258.54	$258.55	$258.50
Purchase #2	$131.97	11.284%	$146.8615	$146.86	$146.85	$146.90
Purchase #3	$40.71	5.686%	$43.0248	$43.02	$43.00	$43.00
Purchase #4	$213.63	3.722%	$221.5813	$221.58	$221.60	$221.60
Purchase #5	$102.38	3.141%	$105.5958	$105.60	$105.60	$105.60
Purchase #6	$37.95	13.489%	$43.0691	$43.07	$43.05	$43.10
Purchase #7	$137.72	4.835%	$144.3788	$144.38	$144.40	$144.40
7 purchase totals =	$905.03		$963.0510	$963.05	$963.05	$963.10