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 $238.67   9.797%   $262.0525   $262.05   $262.05   $262.10  
  Purchase #2 $198.30   4.732%   $207.6836   $207.68   $207.70   $207.70  
  Purchase #3 $24.92   5.284%   $26.2368   $26.24   $26.25   $26.20  
  Purchase #4 $89.94   4.305%   $93.8119   $93.81   $93.80   $93.80  
  Purchase #5 $174.63   7.795%   $188.2424   $188.24   $188.25   $188.20  
  Purchase #6 $195.28   10.711%   $216.1964   $216.20   $216.20   $216.20  
  Purchase #7 $236.39   10.351%   $260.8587   $260.86   $260.85   $260.90  
  7 purchase totals = $1,158.13       $1,255.0823   $1,255.08   $1,255.10   $1,255.10