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 $167.60   5.422%   $176.6873   $176.69   $176.70   $176.70  
  Purchase #2 $240.53   9.223%   $262.7141   $262.71   $262.70   $262.70  
  Purchase #3 $63.29   8.163%   $68.4564   $68.46   $68.45   $68.50  
  Purchase #4 $29.35   5.240%   $30.8879   $30.89   $30.90   $30.90  
  Purchase #5 $70.80   9.269%   $77.3625   $77.36   $77.35   $77.40  
  Purchase #6 $70.86   8.212%   $76.679   $76.68   $76.70   $76.70  
  Purchase #7 $95.86   7.648%   $103.1914   $103.19   $103.20   $103.20  
  7 purchase totals = $738.29       $795.9786   $795.98   $796.00   $796.10