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 $78.51   10.727%   $86.9318   $86.93   $86.95   $86.90  
  Purchase #2 $49.89   5.238%   $52.5032   $52.50   $52.50   $52.50  
  Purchase #3 $44.90   4.534%   $46.9358   $46.94   $46.95   $46.90  
  Purchase #4 $109.69   8.808%   $119.3515   $119.35   $119.35   $119.40  
  Purchase #5 $33.84   6.682%   $36.1012   $36.10   $36.10   $36.10  
  Purchase #6 $191.98   10.718%   $212.5564   $212.56   $212.55   $212.60  
  Purchase #7 $193.88   7.738%   $208.8824   $208.88   $208.90   $208.90  
  7 purchase totals = $702.69       $763.2623   $763.26   $763.30   $763.30