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	$112.28	13.585%	$127.5332	$127.53	$127.55	$127.50
Purchase #2	$200.83	8.215%	$217.3282	$217.33	$217.35	$217.30
Purchase #3	$211.94	7.428%	$227.6829	$227.68	$227.70	$227.70
Purchase #4	$69.52	3.526%	$71.9713	$71.97	$71.95	$72.00
Purchase #5	$230.29	4.770%	$241.2748	$241.27	$241.25	$241.30
Purchase #6	$211.53	5.318%	$222.7792	$222.78	$222.80	$222.80
Purchase #7	$40.76	7.639%	$43.8737	$43.87	$43.85	$43.90
7 purchase totals =	$1,077.15		$1,152.4433	$1,152.43	$1,152.45	$1,152.50