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	$139.25	9.518%	$152.5038	$152.50	$152.50	$152.50
Purchase #2	$103.46	13.694%	$117.6278	$117.63	$117.65	$117.60
Purchase #3	$208.91	12.862%	$235.78	$235.78	$235.80	$235.80
Purchase #4	$127.47	13.194%	$144.2884	$144.29	$144.30	$144.30
Purchase #5	$167.35	9.109%	$182.5939	$182.59	$182.60	$182.60
Purchase #6	$100.74	13.748%	$114.5897	$114.59	$114.60	$114.60
Purchase #7	$77.91	4.187%	$81.1721	$81.17	$81.15	$81.20
7 purchase totals =	$925.09		$1,028.5557	$1,028.55	$1,028.60	$1,028.60