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	$23.47	11.860%	$26.2535	$26.25	$26.25	$26.30
Purchase #2	$172.27	11.413%	$191.9312	$191.93	$191.95	$191.90
Purchase #3	$100.58	11.813%	$112.4615	$112.46	$112.45	$112.50
Purchase #4	$54.83	3.630%	$56.8203	$56.82	$56.80	$56.80
Purchase #5	$250.62	12.734%	$282.534	$282.53	$282.55	$282.50
Purchase #6	$113.94	7.799%	$122.8262	$122.83	$122.85	$122.80
Purchase #7	$80.74	12.194%	$90.5854	$90.59	$90.60	$90.60
7 purchase totals =	$796.45		$883.4121	$883.41	$883.45	$883.40