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 $58.75   5.799%   $62.1569   $62.16   $62.15   $62.20  
  Purchase #2 $108.47   5.461%   $114.3935   $114.39   $114.40   $114.40  
  Purchase #3 $144.59   5.660%   $152.7738   $152.77   $152.75   $152.80  
  Purchase #4 $154.36   5.640%   $163.0659   $163.07   $163.05   $163.10  
  Purchase #5 $247.27   9.699%   $271.2527   $271.25   $271.25   $271.30  
  Purchase #6 $23.46   11.568%   $26.1739   $26.17   $26.15   $26.20  
  Purchase #7 $161.94   3.275%   $167.2435   $167.24   $167.25   $167.20  
  7 purchase totals = $898.84       $957.0602   $957.05   $957.00   $957.20