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 $93.66   4.622%   $97.989   $97.99   $98.00   $98.00  
  Purchase #2 $231.54   4.412%   $241.7555   $241.76   $241.75   $241.80  
  Purchase #3 $179.67   6.620%   $191.5642   $191.56   $191.55   $191.60  
  Purchase #4 $82.44   8.661%   $89.5801   $89.58   $89.60   $89.60  
  Purchase #5 $178.88   9.603%   $196.0578   $196.06   $196.05   $196.10  
  Purchase #6 $165.91   13.317%   $188.0042   $188.00   $188.00   $188.00  
  Purchase #7 $114.33   9.857%   $125.5995   $125.60   $125.60   $125.60  
  7 purchase totals = $1,046.43       $1,130.5503   $1,130.55   $1,130.55   $1,130.70