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 $83.32   12.460%   $93.7017   $93.70   $93.70   $93.70  
  Purchase #2 $137.26   4.659%   $143.6549   $143.65   $143.65   $143.70  
  Purchase #3 $174.62   13.815%   $198.7438   $198.74   $198.75   $198.70  
  Purchase #4 $56.64   5.163%   $59.5643   $59.56   $59.55   $59.60  
  Purchase #5 $168.95   11.563%   $188.4857   $188.49   $188.50   $188.50  
  Purchase #6 $217.67   10.191%   $239.8527   $239.85   $239.85   $239.90  
  Purchase #7 $89.55   13.277%   $101.4396   $101.44   $101.45   $101.40  
  7 purchase totals = $928.01       $1,025.4427   $1,025.43   $1,025.45   $1,025.50