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 $164.54   5.448%   $173.5041   $173.50   $173.50   $173.50  
  Purchase #2 $229.43   13.107%   $259.5014   $259.50   $259.50   $259.50  
  Purchase #3 $141.45   3.849%   $146.8944   $146.89   $146.90   $146.90  
  Purchase #4 $156.50   5.462%   $165.048   $165.05   $165.05   $165.00  
  Purchase #5 $15.69   8.594%   $17.0384   $17.04   $17.05   $17.00  
  Purchase #6 $166.48   6.344%   $177.0415   $177.04   $177.05   $177.00  
  Purchase #7 $127.61   8.217%   $138.0957   $138.10   $138.10   $138.10  
  7 purchase totals = $1,001.70       $1,077.1235   $1,077.12   $1,077.15   $1,077.00