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 $56.69   7.249%   $60.7995   $60.80   $60.80   $60.80  
  Purchase #2 $196.48   6.412%   $209.0783   $209.08   $209.10   $209.10  
  Purchase #3 $179.47   12.102%   $201.1895   $201.19   $201.20   $201.20  
  Purchase #4 $169.95   3.271%   $175.5091   $175.51   $175.50   $175.50  
  Purchase #5 $175.94   9.793%   $193.1698   $193.17   $193.15   $193.20  
  Purchase #6 $119.80   4.516%   $125.2102   $125.21   $125.20   $125.20  
  Purchase #7 $61.49   11.221%   $68.3898   $68.39   $68.40   $68.40  
  7 purchase totals = $959.82       $1,033.3462   $1,033.35   $1,033.35   $1,033.40