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 $167.53   11.574%   $186.9199   $186.92   $186.90   $186.90  
  Purchase #2 $185.39   12.241%   $208.0836   $208.08   $208.10   $208.10  
  Purchase #3 $13.69   11.504%   $15.2649   $15.26   $15.25   $15.30  
  Purchase #4 $175.54   11.776%   $196.2116   $196.21   $196.20   $196.20  
  Purchase #5 $34.47   4.584%   $36.0501   $36.05   $36.05   $36.10  
  Purchase #6 $83.45   9.206%   $91.1324   $91.13   $91.15   $91.10  
  Purchase #7 $200.45   9.217%   $218.9255   $218.93   $218.95   $218.90  
  7 purchase totals = $860.52       $952.5880   $952.58   $952.60   $952.60