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 $112.73   4.671%   $117.9956   $118.00   $118.00   $118.00  
  Purchase #2 $24.77   5.165%   $26.0494   $26.05   $26.05   $26.00  
  Purchase #3 $145.86   4.544%   $152.4879   $152.49   $152.50   $152.50  
  Purchase #4 $246.77   9.161%   $269.3766   $269.38   $269.40   $269.40  
  Purchase #5 $90.88   6.382%   $96.68   $96.68   $96.70   $96.70  
  Purchase #6 $49.68   5.580%   $52.4521   $52.45   $52.45   $52.50  
  Purchase #7 $209.63   10.615%   $231.8822   $231.88   $231.90   $231.90  
  7 purchase totals = $880.32       $946.9238   $946.93   $947.00   $947.00