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	$95.40	7.263%	$102.3289	$102.33	$102.35	$102.30
Purchase #2	$231.47	3.509%	$239.5923	$239.59	$239.60	$239.60
Purchase #3	$137.84	4.192%	$143.6183	$143.62	$143.60	$143.60
Purchase #4	$84.76	7.281%	$90.9314	$90.93	$90.95	$90.90
Purchase #5	$177.60	9.663%	$194.7615	$194.76	$194.75	$194.80
Purchase #6	$57.25	7.514%	$61.5518	$61.55	$61.55	$61.60
Purchase #7	$166.32	10.713%	$184.1379	$184.14	$184.15	$184.10
7 purchase totals =	$950.64		$1,016.9221	$1,016.92	$1,016.95	$1,016.90