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 $214.86   8.864%   $233.9052   $233.91   $233.90   $233.90  
  Purchase #2 $40.84   8.478%   $44.3024   $44.30   $44.30   $44.30  
  Purchase #3 $186.35   5.532%   $196.6589   $196.66   $196.65   $196.70  
  Purchase #4 $189.59   13.273%   $214.7543   $214.75   $214.75   $214.80  
  Purchase #5 $227.46   8.261%   $246.2505   $246.25   $246.25   $246.30  
  Purchase #6 $15.40   11.828%   $17.2215   $17.22   $17.20   $17.20  
  Purchase #7 $50.45   8.727%   $54.8528   $54.85   $54.85   $54.90  
  7 purchase totals = $924.95       $1,007.9456   $1,007.94   $1,007.90   $1,008.10