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	$42.46	7.144%	$45.4933	$45.49	$45.50	$45.50
Purchase #2	$112.86	7.328%	$121.1304	$121.13	$121.15	$121.10
Purchase #3	$166.27	3.105%	$171.4327	$171.43	$171.45	$171.40
Purchase #4	$239.85	9.503%	$262.6429	$262.64	$262.65	$262.60
Purchase #5	$146.64	4.653%	$153.4632	$153.46	$153.45	$153.50
Purchase #6	$28.60	10.451%	$31.589	$31.59	$31.60	$31.60
Purchase #7	$9.55	12.552%	$10.7487	$10.75	$10.75	$10.70
7 purchase totals =	$746.23		$796.5002	$796.49	$796.55	$796.40