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 $59.82   8.659%   $64.9998   $65.00   $65.00   $65.00  
  Purchase #2 $213.30   5.367%   $224.7478   $224.75   $224.75   $224.70  
  Purchase #3 $201.66   12.588%   $227.045   $227.05   $227.05   $227.00  
  Purchase #4 $127.80   8.168%   $138.2387   $138.24   $138.25   $138.20  
  Purchase #5 $175.61   10.687%   $194.3774   $194.38   $194.40   $194.40  
  Purchase #6 $237.62   4.815%   $249.0614   $249.06   $249.05   $249.10  
  Purchase #7 $56.75   12.565%   $63.8806   $63.88   $63.90   $63.90  
  7 purchase totals = $1,072.56       $1,162.3507   $1,162.36   $1,162.40   $1,162.30