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 $243.38   7.733%   $262.2006   $262.20   $262.20   $262.20  
  Purchase #2 $62.66   3.697%   $64.9765   $64.98   $65.00   $65.00  
  Purchase #3 $190.98   5.870%   $202.1905   $202.19   $202.20   $202.20  
  Purchase #4 $154.48   10.298%   $170.3884   $170.39   $170.40   $170.40  
  Purchase #5 $186.73   3.794%   $193.8145   $193.81   $193.80   $193.80  
  Purchase #6 $230.47   12.594%   $259.4954   $259.50   $259.50   $259.50  
  Purchase #7 $14.53   13.851%   $16.5426   $16.54   $16.55   $16.50  
  7 purchase totals = $1,083.23       $1,169.6085   $1,169.61   $1,169.65   $1,169.60