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 $239.71   9.571%   $262.6526   $262.65   $262.65   $262.70  
  Purchase #2 $31.78   6.871%   $33.9636   $33.96   $33.95   $34.00  
  Purchase #3 $216.40   12.215%   $242.8333   $242.83   $242.85   $242.80  
  Purchase #4 $198.91   9.220%   $217.2495   $217.25   $217.25   $217.20  
  Purchase #5 $19.82   9.198%   $21.643   $21.64   $21.65   $21.60  
  Purchase #6 $166.46   4.125%   $173.3265   $173.33   $173.35   $173.30  
  Purchase #7 $208.69   4.566%   $218.2188   $218.22   $218.20   $218.20  
  7 purchase totals = $1,081.77       $1,169.8873   $1,169.88   $1,169.90   $1,169.80