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 $108.33   5.278%   $114.0477   $114.05   $114.05   $114.00  
  Purchase #2 $188.83   8.112%   $204.1479   $204.15   $204.15   $204.10  
  Purchase #3 $7.41   11.581%   $8.2682   $8.27   $8.25   $8.30  
  Purchase #4 $93.26   9.789%   $102.3892   $102.39   $102.40   $102.40  
  Purchase #5 $225.41   4.224%   $234.9313   $234.93   $234.95   $234.90  
  Purchase #6 $25.48   3.822%   $26.4538   $26.45   $26.45   $26.50  
  Purchase #7 $32.97   10.186%   $36.3283   $36.33   $36.35   $36.30  
  7 purchase totals = $681.69       $726.5664   $726.57   $726.60   $726.50