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 $90.86   5.255%   $95.6347   $95.63   $95.65   $95.60  
  Purchase #2 $192.99   11.586%   $215.3498   $215.35   $215.35   $215.30  
  Purchase #3 $247.51   5.669%   $261.5413   $261.54   $261.55   $261.50  
  Purchase #4 $242.65   5.838%   $256.8159   $256.82   $256.80   $256.80  
  Purchase #5 $130.66   13.290%   $148.0247   $148.02   $148.00   $148.00  
  Purchase #6 $205.30   12.347%   $230.6484   $230.65   $230.65   $230.60  
  Purchase #7 $224.46   8.158%   $242.7714   $242.77   $242.75   $242.80  
  7 purchase totals = $1,334.43       $1,450.7862   $1,450.78   $1,450.75   $1,450.60