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 $87.60   8.558%   $95.0968   $95.10   $95.10   $95.10  
  Purchase #2 $114.48   10.623%   $126.6412   $126.64   $126.65   $126.60  
  Purchase #3 $48.61   12.194%   $54.5375   $54.54   $54.55   $54.50  
  Purchase #4 $22.84   5.786%   $24.1615   $24.16   $24.15   $24.20  
  Purchase #5 $136.38   10.154%   $150.228   $150.23   $150.25   $150.20  
  Purchase #6 $27.39   5.493%   $28.8945   $28.89   $28.90   $28.90  
  Purchase #7 $245.63   4.269%   $256.1159   $256.12   $256.10   $256.10  
  7 purchase totals = $682.93       $735.6754   $735.68   $735.70   $735.60