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 $68.75   6.750%   $73.3906   $73.39   $73.40   $73.40  
  Purchase #2 $173.81   11.357%   $193.5496   $193.55   $193.55   $193.50  
  Purchase #3 $248.37   7.488%   $266.9679   $266.97   $266.95   $267.00  
  Purchase #4 $167.44   9.167%   $182.7892   $182.79   $182.80   $182.80  
  Purchase #5 $232.44   5.744%   $245.7914   $245.79   $245.80   $245.80  
  Purchase #6 $56.98   11.231%   $63.3794   $63.38   $63.40   $63.40  
  Purchase #7 $193.79   8.850%   $210.9404   $210.94   $210.95   $210.90  
  7 purchase totals = $1,141.58       $1,236.8085   $1,236.81   $1,236.85   $1,236.80