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	$22.37	7.348%	$24.0137	$24.01	$24.00	$24.00
Purchase #2	$49.27	6.696%	$52.5691	$52.57	$52.55	$52.60
Purchase #3	$218.40	4.202%	$227.5772	$227.58	$227.60	$227.60
Purchase #4	$66.74	7.614%	$71.8216	$71.82	$71.80	$71.80
Purchase #5	$86.69	3.596%	$89.8074	$89.81	$89.80	$89.80
Purchase #6	$133.64	6.106%	$141.8001	$141.80	$141.80	$141.80
Purchase #7	$113.65	5.495%	$119.8951	$119.90	$119.90	$119.90
7 purchase totals =	$690.76		$727.4842	$727.49	$727.45	$727.50