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 $60.95   3.322%   $62.9748   $62.97   $62.95   $63.00  
  Purchase #2 $249.47   5.408%   $262.9613   $262.96   $262.95   $263.00  
  Purchase #3 $80.53   5.231%   $84.7425   $84.74   $84.75   $84.70  
  Purchase #4 $26.38   11.236%   $29.3441   $29.34   $29.35   $29.30  
  Purchase #5 $209.84   13.455%   $238.074   $238.07   $238.05   $238.10  
  Purchase #6 $127.55   7.448%   $137.0499   $137.05   $137.05   $137.00  
  Purchase #7 $131.58   9.863%   $144.5577   $144.56   $144.55   $144.60  
  7 purchase totals = $886.30       $959.7043   $959.69   $959.65   $959.70