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 $173.63   13.202%   $196.5526   $196.55   $196.55   $196.60  
  Purchase #2 $208.47   10.151%   $229.6318   $229.63   $229.65   $229.60  
  Purchase #3 $121.96   4.839%   $127.8616   $127.86   $127.85   $127.90  
  Purchase #4 $248.60   7.479%   $267.1928   $267.19   $267.20   $267.20  
  Purchase #5 $89.37   5.241%   $94.0539   $94.05   $94.05   $94.10  
  Purchase #6 $62.28   6.235%   $66.1632   $66.16   $66.15   $66.20  
  Purchase #7 $74.89   3.226%   $77.306   $77.31   $77.30   $77.30  
  7 purchase totals = $979.20       $1,058.7619   $1,058.75   $1,058.75   $1,058.90