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 $216.70   3.796%   $224.9259   $224.93   $224.95   $224.90  
  Purchase #2 $57.39   5.568%   $60.5855   $60.59   $60.60   $60.60  
  Purchase #3 $69.41   10.506%   $76.7022   $76.70   $76.70   $76.70  
  Purchase #4 $222.85   9.483%   $243.9829   $243.98   $244.00   $244.00  
  Purchase #5 $241.30   13.357%   $273.5304   $273.53   $273.55   $273.50  
  Purchase #6 $237.33   11.602%   $264.865   $264.87   $264.85   $264.90  
  Purchase #7 $240.39   7.281%   $257.8928   $257.89   $257.90   $257.90  
  7 purchase totals = $1,285.37       $1,402.4847   $1,402.49   $1,402.55   $1,402.50