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 $87.26   11.843%   $97.5942   $97.59   $97.60   $97.60  
  Purchase #2 $241.66   5.565%   $255.1084   $255.11   $255.10   $255.10  
  Purchase #3 $194.56   8.866%   $211.8097   $211.81   $211.80   $211.80  
  Purchase #4 $15.58   10.346%   $17.1919   $17.19   $17.20   $17.20  
  Purchase #5 $249.54   3.416%   $258.0643   $258.06   $258.05   $258.10  
  Purchase #6 $10.30   6.671%   $10.9871   $10.99   $11.00   $11.00  
  Purchase #7 $160.38   7.383%   $172.2209   $172.22   $172.20   $172.20  
  7 purchase totals = $959.28       $1,022.9765   $1,022.97   $1,022.95   $1,023.00