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 $222.29   5.863%   $235.3229   $235.32   $235.30   $235.30  
  Purchase #2 $240.66   11.696%   $268.8076   $268.81   $268.80   $268.80  
  Purchase #3 $99.84   13.186%   $113.0049   $113.00   $113.00   $113.00  
  Purchase #4 $242.31   6.677%   $258.489   $258.49   $258.50   $258.50  
  Purchase #5 $110.38   13.193%   $124.9424   $124.94   $124.95   $124.90  
  Purchase #6 $58.55   5.340%   $61.6766   $61.68   $61.70   $61.70  
  Purchase #7 $59.36   8.374%   $64.3308   $64.33   $64.35   $64.30  
  7 purchase totals = $1,033.39       $1,126.5742   $1,126.57   $1,126.60   $1,126.50