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 $85.59   8.583%   $92.9362   $92.94   $92.95   $92.90  
  Purchase #2 $156.65   12.318%   $175.9461   $175.95   $175.95   $175.90  
  Purchase #3 $83.70   3.160%   $86.3449   $86.34   $86.35   $86.30  
  Purchase #4 $132.68   13.256%   $150.2681   $150.27   $150.25   $150.30  
  Purchase #5 $67.57   11.802%   $75.5446   $75.54   $75.55   $75.50  
  Purchase #6 $113.87   8.853%   $123.9509   $123.95   $123.95   $124.00  
  Purchase #7 $163.37   11.497%   $182.1526   $182.15   $182.15   $182.20  
  7 purchase totals = $803.43       $887.1434   $887.14   $887.15   $887.10