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 $40.31   9.110%   $43.9822   $43.98   $44.00   $44.00  
  Purchase #2 $192.94   10.776%   $213.7312   $213.73   $213.75   $213.70  
  Purchase #3 $230.86   5.619%   $243.832   $243.83   $243.85   $243.80  
  Purchase #4 $21.64   8.498%   $23.479   $23.48   $23.50   $23.50  
  Purchase #5 $198.65   10.186%   $218.8845   $218.88   $218.90   $218.90  
  Purchase #6 $227.78   13.794%   $259.2   $259.20   $259.20   $259.20  
  Purchase #7 $240.81   3.599%   $249.4768   $249.48   $249.50   $249.50  
  7 purchase totals = $1,152.99       $1,252.5857   $1,252.58   $1,252.70   $1,252.60