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 $59.36   4.371%   $61.9546   $61.95   $61.95   $62.00  
  Purchase #2 $234.63   6.758%   $250.4863   $250.49   $250.50   $250.50  
  Purchase #3 $85.70   8.424%   $92.9194   $92.92   $92.90   $92.90  
  Purchase #4 $234.43   8.394%   $254.1081   $254.11   $254.10   $254.10  
  Purchase #5 $102.27   13.815%   $116.3986   $116.40   $116.40   $116.40  
  Purchase #6 $131.49   12.861%   $148.4009   $148.40   $148.40   $148.40  
  Purchase #7 $72.61   12.684%   $81.8199   $81.82   $81.80   $81.80  
  7 purchase totals = $920.49       $1,006.0878   $1,006.09   $1,006.05   $1,006.10