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 $32.29   7.379%   $34.6727   $34.67   $34.65   $34.70  
  Purchase #2 $195.44   6.288%   $207.7293   $207.73   $207.75   $207.70  
  Purchase #3 $248.64   9.760%   $272.9073   $272.91   $272.90   $272.90  
  Purchase #4 $53.91   13.571%   $61.2261   $61.23   $61.25   $61.20  
  Purchase #5 $156.32   13.597%   $177.5748   $177.57   $177.55   $177.60  
  Purchase #6 $72.25   5.810%   $76.4477   $76.45   $76.45   $76.40  
  Purchase #7 $166.71   10.149%   $183.6294   $183.63   $183.65   $183.60  
  7 purchase totals = $925.56       $1,014.1873   $1,014.19   $1,014.20   $1,014.10