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 $177.54   9.866%   $195.0561   $195.06   $195.05   $195.10  
  Purchase #2 $69.41   3.693%   $71.9733   $71.97   $71.95   $72.00  
  Purchase #3 $16.57   3.108%   $17.085   $17.09   $17.10   $17.10  
  Purchase #4 $95.26   8.538%   $103.3933   $103.39   $103.40   $103.40  
  Purchase #5 $126.83   7.811%   $136.7367   $136.74   $136.75   $136.70  
  Purchase #6 $233.62   6.507%   $248.8217   $248.82   $248.80   $248.80  
  Purchase #7 $58.74   5.833%   $62.1663   $62.17   $62.15   $62.20  
  7 purchase totals = $777.97       $835.2324   $835.24   $835.20   $835.30