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 $214.76   10.787%   $237.9262   $237.93   $237.95   $237.90  
  Purchase #2 $112.98   6.827%   $120.6931   $120.69   $120.70   $120.70  
  Purchase #3 $59.71   8.158%   $64.5811   $64.58   $64.60   $64.60  
  Purchase #4 $94.45   4.767%   $98.9524   $98.95   $98.95   $99.00  
  Purchase #5 $80.67   13.526%   $91.5814   $91.58   $91.60   $91.60  
  Purchase #6 $81.78   13.576%   $92.8825   $92.88   $92.90   $92.90  
  Purchase #7 $162.50   13.867%   $185.0339   $185.03   $185.05   $185.00  
  7 purchase totals = $806.85       $891.6506   $891.64   $891.75   $891.70