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 $241.70   8.295%   $261.749   $261.75   $261.75   $261.70  
  Purchase #2 $198.86   10.764%   $220.2653   $220.27   $220.25   $220.30  
  Purchase #3 $63.48   10.655%   $70.2438   $70.24   $70.25   $70.20  
  Purchase #4 $117.68   11.738%   $131.4933   $131.49   $131.50   $131.50  
  Purchase #5 $184.72   11.759%   $206.4412   $206.44   $206.45   $206.40  
  Purchase #6 $49.35   4.670%   $51.6546   $51.65   $51.65   $51.70  
  Purchase #7 $62.46   9.829%   $68.5992   $68.60   $68.60   $68.60  
  7 purchase totals = $918.25       $1,010.4464   $1,010.44   $1,010.45   $1,010.40