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 $41.45   4.762%   $43.4238   $43.42   $43.40   $43.40  
  Purchase #2 $249.70   11.621%   $278.7176   $278.72   $278.70   $278.70  
  Purchase #3 $230.27   4.523%   $240.6851   $240.69   $240.70   $240.70  
  Purchase #4 $88.58   6.750%   $94.5592   $94.56   $94.55   $94.60  
  Purchase #5 $247.41   6.762%   $264.1399   $264.14   $264.15   $264.10  
  Purchase #6 $210.76   9.715%   $231.2353   $231.24   $231.25   $231.20  
  Purchase #7 $240.95   7.352%   $258.6646   $258.66   $258.65   $258.70  
  7 purchase totals = $1,309.12       $1,411.4255   $1,411.43   $1,411.40   $1,411.40