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 $68.49   9.859%   $75.2424   $75.24   $75.25   $75.20  
  Purchase #2 $139.45   6.245%   $148.1587   $148.16   $148.15   $148.20  
  Purchase #3 $206.36   11.403%   $229.8912   $229.89   $229.90   $229.90  
  Purchase #4 $235.89   8.170%   $255.1622   $255.16   $255.15   $255.20  
  Purchase #5 $219.54   5.775%   $232.2184   $232.22   $232.20   $232.20  
  Purchase #6 $36.44   9.625%   $39.9474   $39.95   $39.95   $39.90  
  Purchase #7 $201.37   11.863%   $225.2585   $225.26   $225.25   $225.30  
  7 purchase totals = $1,107.54       $1,205.8788   $1,205.88   $1,205.85   $1,205.90