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 $87.44   9.488%   $95.7363   $95.74   $95.75   $95.70  
  Purchase #2 $172.98   11.682%   $193.1875   $193.19   $193.20   $193.20  
  Purchase #3 $213.73   6.796%   $228.2551   $228.26   $228.25   $228.30  
  Purchase #4 $174.67   5.286%   $183.9031   $183.90   $183.90   $183.90  
  Purchase #5 $139.58   6.115%   $148.1153   $148.12   $148.10   $148.10  
  Purchase #6 $87.45   9.707%   $95.9388   $95.94   $95.95   $95.90  
  Purchase #7 $236.55   10.711%   $261.8869   $261.89   $261.90   $261.90  
  7 purchase totals = $1,112.40       $1,207.0230   $1,207.04   $1,207.05   $1,207.00