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 $65.25   4.132%   $67.9461   $67.95   $67.95   $67.90  
  Purchase #2 $218.87   13.182%   $247.7214   $247.72   $247.70   $247.70  
  Purchase #3 $7.26   13.495%   $8.2397   $8.24   $8.25   $8.20  
  Purchase #4 $161.34   7.835%   $173.981   $173.98   $174.00   $174.00  
  Purchase #5 $77.26   5.721%   $81.68   $81.68   $81.70   $81.70  
  Purchase #6 $170.46   9.177%   $186.1031   $186.10   $186.10   $186.10  
  Purchase #7 $108.58   8.496%   $117.805   $117.81   $117.80   $117.80  
  7 purchase totals = $809.02       $883.4763   $883.48   $883.50   $883.40