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 $88.76   7.428%   $95.3531   $95.35   $95.35   $95.40  
  Purchase #2 $202.43   3.673%   $209.8653   $209.87   $209.85   $209.90  
  Purchase #3 $205.45   4.684%   $215.0733   $215.07   $215.05   $215.10  
  Purchase #4 $237.70   8.361%   $257.5741   $257.57   $257.55   $257.60  
  Purchase #5 $201.87   11.812%   $225.7149   $225.71   $225.70   $225.70  
  Purchase #6 $9.64   10.223%   $10.6255   $10.63   $10.65   $10.60  
  Purchase #7 $50.57   4.803%   $52.9989   $53.00   $53.00   $53.00  
  7 purchase totals = $996.42       $1,067.2051   $1,067.20   $1,067.15   $1,067.30