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 $68.89   3.435%   $71.2564   $71.26   $71.25   $71.30  
  Purchase #2 $211.55   11.275%   $235.4023   $235.40   $235.40   $235.40  
  Purchase #3 $62.78   11.589%   $70.0556   $70.06   $70.05   $70.10  
  Purchase #4 $115.35   8.325%   $124.9529   $124.95   $124.95   $125.00  
  Purchase #5 $118.28   5.328%   $124.582   $124.58   $124.60   $124.60  
  Purchase #6 $198.95   13.128%   $225.0682   $225.07   $225.05   $225.10  
  Purchase #7 $97.36   8.334%   $105.474   $105.47   $105.45   $105.50  
  7 purchase totals = $873.16       $956.7914   $956.79   $956.75   $957.00