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 $71.49   7.623%   $76.9397   $76.94   $76.95   $76.90  
  Purchase #2 $109.97   6.397%   $117.0048   $117.00   $117.00   $117.00  
  Purchase #3 $157.83   4.769%   $165.3569   $165.36   $165.35   $165.40  
  Purchase #4 $85.62   12.544%   $96.3602   $96.36   $96.35   $96.40  
  Purchase #5 $25.72   6.816%   $27.4731   $27.47   $27.45   $27.50  
  Purchase #6 $107.97   6.472%   $114.9578   $114.96   $114.95   $115.00  
  Purchase #7 $77.41   8.362%   $83.883   $83.88   $83.90   $83.90  
  7 purchase totals = $636.01       $681.9755   $681.97   $681.95   $682.10