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 $151.96   8.558%   $164.9647   $164.96   $164.95   $165.00  
  Purchase #2 $247.68   4.493%   $258.8083   $258.81   $258.80   $258.80  
  Purchase #3 $91.70   10.328%   $101.1708   $101.17   $101.15   $101.20  
  Purchase #4 $196.54   4.697%   $205.7715   $205.77   $205.75   $205.80  
  Purchase #5 $51.45   10.657%   $56.933   $56.93   $56.95   $56.90  
  Purchase #6 $119.89   12.457%   $134.8247   $134.82   $134.80   $134.80  
  Purchase #7 $84.81   4.645%   $88.7494   $88.75   $88.75   $88.70  
  7 purchase totals = $944.03       $1,011.2224   $1,011.21   $1,011.15   $1,011.20