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 $213.76   6.289%   $227.2034   $227.20   $227.20   $227.20  
  Purchase #2 $105.31   13.317%   $119.3341   $119.33   $119.35   $119.30  
  Purchase #3 $78.79   4.565%   $82.3868   $82.39   $82.40   $82.40  
  Purchase #4 $222.46   13.150%   $251.7135   $251.71   $251.70   $251.70  
  Purchase #5 $164.73   10.533%   $182.081   $182.08   $182.10   $182.10  
  Purchase #6 $22.73   6.634%   $24.2379   $24.24   $24.25   $24.20  
  Purchase #7 $199.46   13.162%   $225.7129   $225.71   $225.70   $225.70  
  7 purchase totals = $1,007.24       $1,112.6696   $1,112.66   $1,112.70   $1,112.60