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 $196.36   6.257%   $208.6462   $208.65   $208.65   $208.60  
  Purchase #2 $126.31   5.779%   $133.6095   $133.61   $133.60   $133.60  
  Purchase #3 $183.49   6.154%   $194.782   $194.78   $194.80   $194.80  
  Purchase #4 $151.81   10.695%   $168.0461   $168.05   $168.05   $168.00  
  Purchase #5 $238.68   6.726%   $254.7336   $254.73   $254.75   $254.70  
  Purchase #6 $78.75   10.459%   $86.9865   $86.99   $87.00   $87.00  
  Purchase #7 $143.46   3.446%   $148.4036   $148.40   $148.40   $148.40  
  7 purchase totals = $1,118.86       $1,195.2075   $1,195.21   $1,195.25   $1,195.10