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 $162.75   12.168%   $182.5534   $182.55   $182.55   $182.60  
  Purchase #2 $206.82   5.569%   $218.3378   $218.34   $218.35   $218.30  
  Purchase #3 $238.92   9.815%   $262.37   $262.37   $262.35   $262.40  
  Purchase #4 $111.94   6.729%   $119.4724   $119.47   $119.45   $119.50  
  Purchase #5 $196.97   5.247%   $207.305   $207.31   $207.30   $207.30  
  Purchase #6 $123.98   10.646%   $137.1789   $137.18   $137.20   $137.20  
  Purchase #7 $86.57   10.241%   $95.4356   $95.44   $95.45   $95.40  
  7 purchase totals = $1,127.95       $1,222.6531   $1,222.66   $1,222.65   $1,222.70