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 $72.91   4.163%   $75.9452   $75.95   $75.95   $75.90  
  Purchase #2 $245.47   13.159%   $277.7714   $277.77   $277.75   $277.80  
  Purchase #3 $31.98   6.663%   $34.1108   $34.11   $34.10   $34.10  
  Purchase #4 $229.93   3.701%   $238.4397   $238.44   $238.45   $238.40  
  Purchase #5 $241.59   8.309%   $261.6637   $261.66   $261.65   $261.70  
  Purchase #6 $70.40   13.459%   $79.8751   $79.88   $79.90   $79.90  
  Purchase #7 $76.80   13.558%   $87.2125   $87.21   $87.20   $87.20  
  7 purchase totals = $969.08       $1,055.0184   $1,055.02   $1,055.00   $1,055.00