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 $196.57   7.580%   $211.47   $211.47   $211.45   $211.50  
  Purchase #2 $105.44   11.714%   $117.7912   $117.79   $117.80   $117.80  
  Purchase #3 $71.49   13.432%   $81.0925   $81.09   $81.10   $81.10  
  Purchase #4 $175.66   5.648%   $185.5813   $185.58   $185.60   $185.60  
  Purchase #5 $233.67   6.806%   $249.5736   $249.57   $249.55   $249.60  
  Purchase #6 $6.36   4.474%   $6.6445   $6.64   $6.65   $6.60  
  Purchase #7 $191.96   12.423%   $215.8072   $215.81   $215.80   $215.80  
  7 purchase totals = $981.15       $1,067.9603   $1,067.95   $1,067.95   $1,068.00