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 $52.37   11.795%   $58.547   $58.55   $58.55   $58.50  
  Purchase #2 $216.28   4.530%   $226.0775   $226.08   $226.10   $226.10  
  Purchase #3 $140.39   12.293%   $157.6481   $157.65   $157.65   $157.60  
  Purchase #4 $174.83   11.361%   $194.6924   $194.69   $194.70   $194.70  
  Purchase #5 $196.47   5.176%   $206.6393   $206.64   $206.65   $206.60  
  Purchase #6 $151.91   8.382%   $164.6431   $164.64   $164.65   $164.60  
  Purchase #7 $53.97   12.408%   $60.6666   $60.67   $60.65   $60.70  
  7 purchase totals = $986.22       $1,068.9140   $1,068.92   $1,068.95   $1,068.80