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	$34.83	5.615%	$36.7857	$36.79	$36.80	$36.80
Purchase #2	$198.70	12.736%	$224.0064	$224.01	$224.00	$224.00
Purchase #3	$33.80	9.345%	$36.9586	$36.96	$36.95	$37.00
Purchase #4	$151.60	4.243%	$158.0324	$158.03	$158.05	$158.00
Purchase #5	$54.28	9.641%	$59.5131	$59.51	$59.50	$59.50
Purchase #6	$156.34	12.230%	$175.4604	$175.46	$175.45	$175.50
Purchase #7	$227.34	12.755%	$256.3372	$256.34	$256.35	$256.30
7 purchase totals =	$856.89		$947.0938	$947.10	$947.10	$947.10