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	$89.54	6.451%	$95.3162	$95.32	$95.30	$95.30
Purchase #2	$126.36	8.732%	$137.3938	$137.39	$137.40	$137.40
Purchase #3	$24.41	11.423%	$27.1984	$27.20	$27.20	$27.20
Purchase #4	$227.95	12.247%	$255.867	$255.87	$255.85	$255.90
Purchase #5	$35.69	4.358%	$37.2454	$37.25	$37.25	$37.20
Purchase #6	$162.81	13.153%	$184.2244	$184.22	$184.20	$184.20
Purchase #7	$220.65	9.432%	$241.4617	$241.46	$241.45	$241.50
7 purchase totals =	$887.41		$978.7069	$978.71	$978.65	$978.70