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 $214.25   10.411%   $236.5556   $236.56   $236.55   $236.60  
  Purchase #2 $197.51   5.235%   $207.8496   $207.85   $207.85   $207.80  
  Purchase #3 $13.35   7.617%   $14.3669   $14.37   $14.35   $14.40  
  Purchase #4 $161.25   9.266%   $176.1914   $176.19   $176.20   $176.20  
  Purchase #5 $195.46   8.589%   $212.2481   $212.25   $212.25   $212.20  
  Purchase #6 $197.55   11.354%   $219.9798   $219.98   $220.00   $220.00  
  Purchase #7 $131.36   5.687%   $138.8304   $138.83   $138.85   $138.80  
  7 purchase totals = $1,110.73       $1,206.0218   $1,206.03   $1,206.05   $1,206.00