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	$38.84	11.680%	$43.3765	$43.38	$43.40	$43.40
Purchase #2	$171.77	7.645%	$184.9018	$184.90	$184.90	$184.90
Purchase #3	$13.81	12.459%	$15.5306	$15.53	$15.55	$15.50
Purchase #4	$36.59	6.604%	$39.0064	$39.01	$39.00	$39.00
Purchase #5	$164.30	10.248%	$181.1375	$181.14	$181.15	$181.10
Purchase #6	$193.79	7.553%	$208.427	$208.43	$208.45	$208.40
Purchase #7	$210.58	5.828%	$222.8526	$222.85	$222.85	$222.90
7 purchase totals =	$829.68		$895.2324	$895.24	$895.30	$895.20