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 $87.82   8.130%   $94.9598   $94.96   $94.95   $95.00  
  Purchase #2 $114.49   9.395%   $125.2463   $125.25   $125.25   $125.20  
  Purchase #3 $214.51   10.588%   $237.2223   $237.22   $237.20   $237.20  
  Purchase #4 $23.88   9.476%   $26.1429   $26.14   $26.15   $26.10  
  Purchase #5 $123.26   9.472%   $134.9352   $134.94   $134.95   $134.90  
  Purchase #6 $130.43   12.525%   $146.7664   $146.77   $146.75   $146.80  
  Purchase #7 $13.83   12.208%   $15.5184   $15.52   $15.50   $15.50  
  7 purchase totals = $708.22       $780.7913   $780.80   $780.75   $780.70