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 $167.78   4.692%   $175.6522   $175.65   $175.65   $175.70  
  Purchase #2 $59.39   4.350%   $61.9735   $61.97   $61.95   $62.00  
  Purchase #3 $135.96   7.577%   $146.2617   $146.26   $146.25   $146.30  
  Purchase #4 $226.72   11.554%   $252.9152   $252.92   $252.90   $252.90  
  Purchase #5 $81.56   3.274%   $84.2303   $84.23   $84.25   $84.20  
  Purchase #6 $53.87   3.480%   $55.7447   $55.74   $55.75   $55.70  
  Purchase #7 $243.81   6.515%   $259.6942   $259.69   $259.70   $259.70  
  7 purchase totals = $969.09       $1,036.4718   $1,036.46   $1,036.45   $1,036.50