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 $69.82   9.787%   $76.6533   $76.65   $76.65   $76.70  
  Purchase #2 $110.46   8.285%   $119.6116   $119.61   $119.60   $119.60  
  Purchase #3 $148.54   13.212%   $168.1651   $168.17   $168.15   $168.20  
  Purchase #4 $229.39   6.485%   $244.2659   $244.27   $244.25   $244.30  
  Purchase #5 $23.67   10.453%   $26.1442   $26.14   $26.15   $26.10  
  Purchase #6 $223.68   12.662%   $252.0024   $252.00   $252.00   $252.00  
  Purchase #7 $45.99   5.266%   $48.4118   $48.41   $48.40   $48.40  
  7 purchase totals = $851.55       $935.2543   $935.25   $935.20   $935.30