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 $41.36   5.661%   $43.7014   $43.70   $43.70   $43.70  
  Purchase #2 $85.26   7.817%   $91.9248   $91.92   $91.90   $91.90  
  Purchase #3 $67.87   12.789%   $76.5499   $76.55   $76.55   $76.50  
  Purchase #4 $216.50   8.592%   $235.1017   $235.10   $235.10   $235.10  
  Purchase #5 $223.43   12.710%   $251.828   $251.83   $251.85   $251.80  
  Purchase #6 $228.98   3.161%   $236.2181   $236.22   $236.20   $236.20  
  Purchase #7 $42.89   10.590%   $47.4321   $47.43   $47.45   $47.40  
  7 purchase totals = $906.29       $982.7560   $982.75   $982.75   $982.60