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 $97.54   10.737%   $108.0129   $108.01   $108.00   $108.00  
  Purchase #2 $68.60   8.785%   $74.6265   $74.63   $74.65   $74.60  
  Purchase #3 $159.29   7.775%   $171.6748   $171.67   $171.65   $171.70  
  Purchase #4 $246.36   10.820%   $273.0162   $273.02   $273.00   $273.00  
  Purchase #5 $115.43   6.766%   $123.24   $123.24   $123.25   $123.20  
  Purchase #6 $237.81   6.518%   $253.3105   $253.31   $253.30   $253.30  
  Purchase #7 $49.87   10.728%   $55.2201   $55.22   $55.20   $55.20  
  7 purchase totals = $974.90       $1,059.1010   $1,059.10   $1,059.05   $1,059.00