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 $173.51   13.769%   $197.4006   $197.40   $197.40   $197.40  
  Purchase #2 $56.78   11.792%   $63.4755   $63.48   $63.50   $63.50  
  Purchase #3 $119.95   13.628%   $136.2968   $136.30   $136.30   $136.30  
  Purchase #4 $125.62   10.237%   $138.4797   $138.48   $138.50   $138.50  
  Purchase #5 $119.38   4.462%   $124.7067   $124.71   $124.70   $124.70  
  Purchase #6 $170.43   3.790%   $176.8893   $176.89   $176.90   $176.90  
  Purchase #7 $167.30   11.436%   $186.4324   $186.43   $186.45   $186.40  
  7 purchase totals = $932.97       $1,023.6810   $1,023.69   $1,023.75   $1,023.70