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	$225.57	5.291%	$237.5049	$237.50	$237.50	$237.50
Purchase #2	$186.75	6.265%	$198.4499	$198.45	$198.45	$198.40
Purchase #3	$131.27	9.805%	$144.141	$144.14	$144.15	$144.10
Purchase #4	$138.82	9.384%	$151.8469	$151.85	$151.85	$151.80
Purchase #5	$19.89	3.544%	$20.5949	$20.59	$20.60	$20.60
Purchase #6	$224.80	8.385%	$243.6495	$243.65	$243.65	$243.60
Purchase #7	$70.63	4.616%	$73.8903	$73.89	$73.90	$73.90
7 purchase totals =	$997.73		$1,070.0774	$1,070.07	$1,070.10	$1,069.90