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 $55.98   11.245%   $62.275   $62.28   $62.30   $62.30  
  Purchase #2 $144.64   10.801%   $160.2626   $160.26   $160.25   $160.30  
  Purchase #3 $118.64   13.163%   $134.2566   $134.26   $134.25   $134.30  
  Purchase #4 $147.60   5.627%   $155.9055   $155.91   $155.90   $155.90  
  Purchase #5 $54.81   9.586%   $60.0641   $60.06   $60.05   $60.10  
  Purchase #6 $196.69   12.432%   $221.1425   $221.14   $221.15   $221.10  
  Purchase #7 $249.81   9.339%   $273.1398   $273.14   $273.15   $273.10  
  7 purchase totals = $968.17       $1,067.0461   $1,067.05   $1,067.05   $1,067.10