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 $192.83   7.356%   $207.0146   $207.01   $207.00   $207.00  
  Purchase #2 $245.61   12.811%   $277.0751   $277.08   $277.10   $277.10  
  Purchase #3 $242.82   7.859%   $261.9032   $261.90   $261.90   $261.90  
  Purchase #4 $197.88   13.244%   $224.0872   $224.09   $224.10   $224.10  
  Purchase #5 $79.55   8.321%   $86.1694   $86.17   $86.15   $86.20  
  Purchase #6 $163.58   6.648%   $174.4548   $174.45   $174.45   $174.50  
  Purchase #7 $58.91   9.336%   $64.4098   $64.41   $64.40   $64.40  
  7 purchase totals = $1,181.18       $1,295.1141   $1,295.11   $1,295.10   $1,295.20