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 $212.99   5.469%   $224.6384   $224.64   $224.65   $224.60  
  Purchase #2 $43.81   3.550%   $45.3653   $45.37   $45.35   $45.40  
  Purchase #3 $97.83   6.338%   $104.0305   $104.03   $104.05   $104.00  
  Purchase #4 $199.57   8.329%   $216.1922   $216.19   $216.20   $216.20  
  Purchase #5 $217.95   8.570%   $236.6283   $236.63   $236.65   $236.60  
  Purchase #6 $214.94   11.837%   $240.3824   $240.38   $240.40   $240.40  
  Purchase #7 $159.42   3.597%   $165.1543   $165.15   $165.15   $165.20  
  7 purchase totals = $1,146.51       $1,232.3914   $1,232.39   $1,232.45   $1,232.40