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 $86.81   10.623%   $96.0318   $96.03   $96.05   $96.00  
  Purchase #2 $54.62   9.587%   $59.8564   $59.86   $59.85   $59.90  
  Purchase #3 $202.35   11.118%   $224.8473   $224.85   $224.85   $224.80  
  Purchase #4 $80.33   3.870%   $83.4388   $83.44   $83.45   $83.40  
  Purchase #5 $104.65   8.703%   $113.7577   $113.76   $113.75   $113.80  
  Purchase #6 $155.79   13.665%   $177.0787   $177.08   $177.10   $177.10  
  Purchase #7 $11.66   11.537%   $13.0052   $13.01   $13.00   $13.00  
  7 purchase totals = $696.21       $768.0159   $768.03   $768.05   $768.00