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 $88.61   8.825%   $96.4298   $96.43   $96.45   $96.40  
  Purchase #2 $222.62   10.119%   $245.1469   $245.15   $245.15   $245.10  
  Purchase #3 $103.60   13.637%   $117.7279   $117.73   $117.75   $117.70  
  Purchase #4 $119.87   7.758%   $129.1695   $129.17   $129.15   $129.20  
  Purchase #5 $228.85   11.429%   $255.0053   $255.01   $255.00   $255.00  
  Purchase #6 $249.95   3.595%   $258.9357   $258.94   $258.95   $258.90  
  Purchase #7 $47.45   4.706%   $49.683   $49.68   $49.70   $49.70  
  7 purchase totals = $1,060.95       $1,152.0981   $1,152.11   $1,152.15   $1,152.00