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 $46.96   3.594%   $48.6477   $48.65   $48.65   $48.60  
  Purchase #2 $184.55   12.695%   $207.9786   $207.98   $208.00   $208.00  
  Purchase #3 $39.42   3.618%   $40.8462   $40.85   $40.85   $40.80  
  Purchase #4 $52.99   8.715%   $57.6081   $57.61   $57.60   $57.60  
  Purchase #5 $250.25   3.126%   $258.0728   $258.07   $258.05   $258.10  
  Purchase #6 $82.99   6.646%   $88.5055   $88.51   $88.50   $88.50  
  Purchase #7 $227.51   10.513%   $251.4281   $251.43   $251.45   $251.40  
  7 purchase totals = $884.67       $953.0870   $953.10   $953.10   $953.00