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 $114.78   9.712%   $125.9274   $125.93   $125.95   $125.90  
  Purchase #2 $178.80   4.786%   $187.3574   $187.36   $187.35   $187.40  
  Purchase #3 $24.29   9.332%   $26.5567   $26.56   $26.55   $26.60  
  Purchase #4 $190.50   10.221%   $209.971   $209.97   $209.95   $210.00  
  Purchase #5 $13.74   6.413%   $14.6211   $14.62   $14.60   $14.60  
  Purchase #6 $57.48   12.146%   $64.4615   $64.46   $64.45   $64.50  
  Purchase #7 $224.60   5.275%   $236.4477   $236.45   $236.45   $236.40  
  7 purchase totals = $804.19       $865.3428   $865.35   $865.30   $865.40