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 $88.48   8.410%   $95.9212   $95.92   $95.90   $95.90  
  Purchase #2 $237.74   12.579%   $267.6453   $267.65   $267.65   $267.60  
  Purchase #3 $66.39   8.523%   $72.0484   $72.05   $72.05   $72.00  
  Purchase #4 $53.87   8.269%   $58.3245   $58.32   $58.30   $58.30  
  Purchase #5 $116.92   5.696%   $123.5798   $123.58   $123.60   $123.60  
  Purchase #6 $156.93   13.256%   $177.7326   $177.73   $177.75   $177.70  
  Purchase #7 $201.41   4.154%   $209.7766   $209.78   $209.80   $209.80  
  7 purchase totals = $921.74       $1,005.0284   $1,005.03   $1,005.05   $1,004.90