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 $219.62   6.833%   $234.6266   $234.63   $234.65   $234.60  
  Purchase #2 $32.28   13.433%   $36.6162   $36.62   $36.60   $36.60  
  Purchase #3 $133.47   5.223%   $140.4411   $140.44   $140.45   $140.40  
  Purchase #4 $202.54   11.696%   $226.2291   $226.23   $226.25   $226.20  
  Purchase #5 $165.31   6.214%   $175.5824   $175.58   $175.60   $175.60  
  Purchase #6 $59.54   3.418%   $61.5751   $61.58   $61.60   $61.60  
  Purchase #7 $192.74   4.655%   $201.712   $201.71   $201.70   $201.70  
  7 purchase totals = $1,005.50       $1,076.7825   $1,076.79   $1,076.85   $1,076.70