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 $221.85   8.498%   $240.7028   $240.70   $240.70   $240.70  
  Purchase #2 $104.44   8.247%   $113.0532   $113.05   $113.05   $113.10  
  Purchase #3 $43.96   5.839%   $46.5268   $46.53   $46.55   $46.50  
  Purchase #4 $176.94   4.613%   $185.1022   $185.10   $185.10   $185.10  
  Purchase #5 $240.35   8.256%   $260.1933   $260.19   $260.20   $260.20  
  Purchase #6 $104.65   8.812%   $113.8718   $113.87   $113.85   $113.90  
  Purchase #7 $224.59   8.864%   $244.4977   $244.50   $244.50   $244.50  
  7 purchase totals = $1,116.78       $1,203.9478   $1,203.94   $1,203.95   $1,204.00