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	$119.93	6.594%	$127.8382	$127.84	$127.85	$127.80
Purchase #2	$76.52	4.580%	$80.0246	$80.02	$80.00	$80.00
Purchase #3	$154.95	11.337%	$172.5167	$172.52	$172.50	$172.50
Purchase #4	$47.85	7.732%	$51.5498	$51.55	$51.55	$51.50
Purchase #5	$225.38	6.770%	$240.6382	$240.64	$240.65	$240.60
Purchase #6	$211.42	12.265%	$237.3507	$237.35	$237.35	$237.40
Purchase #7	$207.81	7.230%	$222.8347	$222.83	$222.85	$222.80
7 purchase totals =	$1,043.86		$1,132.7529	$1,132.75	$1,132.75	$1,132.60