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 $246.32   8.588%   $267.474   $267.47   $267.45   $267.50  
  Purchase #2 $84.39   3.719%   $87.5285   $87.53   $87.55   $87.50  
  Purchase #3 $110.25   12.283%   $123.792   $123.79   $123.80   $123.80  
  Purchase #4 $100.66   4.845%   $105.537   $105.54   $105.55   $105.50  
  Purchase #5 $174.53   6.587%   $186.0263   $186.03   $186.05   $186.00  
  Purchase #6 $152.79   4.519%   $159.6946   $159.69   $159.70   $159.70  
  Purchase #7 $207.37   3.385%   $214.3895   $214.39   $214.40   $214.40  
  7 purchase totals = $1,076.31       $1,144.4419   $1,144.44   $1,144.50   $1,144.40