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 $96.32   6.264%   $102.3535   $102.35   $102.35   $102.40  
  Purchase #2 $232.81   9.373%   $254.6313   $254.63   $254.65   $254.60  
  Purchase #3 $77.32   4.427%   $80.743   $80.74   $80.75   $80.70  
  Purchase #4 $62.62   11.131%   $69.5902   $69.59   $69.60   $69.60  
  Purchase #5 $231.99   10.420%   $256.1634   $256.16   $256.15   $256.20  
  Purchase #6 $60.67   4.588%   $63.4535   $63.45   $63.45   $63.50  
  Purchase #7 $64.65   5.806%   $68.4036   $68.40   $68.40   $68.40  
  7 purchase totals = $826.38       $895.3385   $895.32   $895.35   $895.40