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 $169.66   9.690%   $186.1001   $186.10   $186.10   $186.10  
  Purchase #2 $105.46   7.197%   $113.05   $113.05   $113.05   $113.10  
  Purchase #3 $11.91   13.274%   $13.4909   $13.49   $13.50   $13.50  
  Purchase #4 $32.87   3.834%   $34.1302   $34.13   $34.15   $34.10  
  Purchase #5 $76.76   11.281%   $85.4193   $85.42   $85.40   $85.40  
  Purchase #6 $26.65   5.797%   $28.1949   $28.19   $28.20   $28.20  
  Purchase #7 $232.92   3.317%   $240.646   $240.65   $240.65   $240.60  
  7 purchase totals = $656.23       $701.0314   $701.03   $701.05   $701.00