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	$23.81	7.451%	$25.5841	$25.58	$25.60	$25.60
Purchase #2	$113.51	3.479%	$117.459	$117.46	$117.45	$117.50
Purchase #3	$225.25	7.709%	$242.6145	$242.61	$242.60	$242.60
Purchase #4	$95.59	9.134%	$104.3212	$104.32	$104.30	$104.30
Purchase #5	$103.82	10.642%	$114.8685	$114.87	$114.85	$114.90
Purchase #6	$82.48	4.213%	$85.9549	$85.95	$85.95	$86.00
Purchase #7	$76.62	11.665%	$85.5577	$85.56	$85.55	$85.60
7 purchase totals =	$721.08		$776.3599	$776.35	$776.30	$776.50