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	$217.72	7.726%	$234.541	$234.54	$234.55	$234.50
Purchase #2	$190.86	8.538%	$207.1556	$207.16	$207.15	$207.20
Purchase #3	$214.27	10.549%	$236.8733	$236.87	$236.85	$236.90
Purchase #4	$140.38	8.552%	$152.3853	$152.39	$152.40	$152.40
Purchase #5	$136.71	9.725%	$150.005	$150.01	$150.00	$150.00
Purchase #6	$199.62	11.473%	$222.5224	$222.52	$222.50	$222.50
Purchase #7	$61.72	13.515%	$70.0615	$70.06	$70.05	$70.10
7 purchase totals =	$1,161.28		$1,273.5441	$1,273.55	$1,273.50	$1,273.60