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 $94.76   7.141%   $101.5268   $101.53   $101.55   $101.50  
  Purchase #2 $24.70   5.396%   $26.0328   $26.03   $26.05   $26.00  
  Purchase #3 $233.49   9.510%   $255.6949   $255.69   $255.70   $255.70  
  Purchase #4 $133.60   9.671%   $146.5205   $146.52   $146.50   $146.50  
  Purchase #5 $230.88   8.537%   $250.5902   $250.59   $250.60   $250.60  
  Purchase #6 $74.42   8.270%   $80.5745   $80.57   $80.55   $80.60  
  Purchase #7 $193.91   10.690%   $214.639   $214.64   $214.65   $214.60  
  7 purchase totals = $985.76       $1,075.5787   $1,075.57   $1,075.60   $1,075.50