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 $237.81   11.490%   $265.1344   $265.13   $265.15   $265.10  
  Purchase #2 $136.60   11.533%   $152.3541   $152.35   $152.35   $152.40  
  Purchase #3 $225.92   4.579%   $236.2649   $236.26   $236.25   $236.30  
  Purchase #4 $68.40   12.574%   $77.0006   $77.00   $77.00   $77.00  
  Purchase #5 $194.39   11.823%   $217.3727   $217.37   $217.35   $217.40  
  Purchase #6 $50.56   11.263%   $56.2546   $56.25   $56.25   $56.30  
  Purchase #7 $60.68   4.112%   $63.1752   $63.18   $63.20   $63.20  
  7 purchase totals = $974.36       $1,067.5565   $1,067.54   $1,067.55   $1,067.70