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	$222.71	10.397%	$245.8652	$245.87	$245.85	$245.90
Purchase #2	$187.39	4.829%	$196.4391	$196.44	$196.45	$196.40
Purchase #3	$123.74	11.154%	$137.542	$137.54	$137.55	$137.50
Purchase #4	$115.42	8.770%	$125.5423	$125.54	$125.55	$125.50
Purchase #5	$65.80	7.755%	$70.9028	$70.90	$70.90	$70.90
Purchase #6	$118.53	11.821%	$132.5414	$132.54	$132.55	$132.50
Purchase #7	$92.95	12.800%	$104.8476	$104.85	$104.85	$104.80
7 purchase totals =	$926.54		$1,013.6804	$1,013.68	$1,013.70	$1,013.50