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 $60.30   7.676%   $64.9286   $64.93   $64.95   $64.90  
  Purchase #2 $176.54   3.526%   $182.7648   $182.76   $182.75   $182.80  
  Purchase #3 $179.75   12.224%   $201.7226   $201.72   $201.70   $201.70  
  Purchase #4 $234.27   9.836%   $257.3128   $257.31   $257.30   $257.30  
  Purchase #5 $232.91   5.477%   $245.6665   $245.67   $245.65   $245.70  
  Purchase #6 $219.78   6.491%   $234.0459   $234.05   $234.05   $234.00  
  Purchase #7 $7.32   3.672%   $7.5888   $7.59   $7.60   $7.60  
  7 purchase totals = $1,110.87       $1,194.0300   $1,194.03   $1,194.00   $1,194.00