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 $46.26   9.692%   $50.7435   $50.74   $50.75   $50.70  
  Purchase #2 $122.43   11.670%   $136.7176   $136.72   $136.70   $136.70  
  Purchase #3 $177.41   13.562%   $201.4703   $201.47   $201.45   $201.50  
  Purchase #4 $65.34   10.419%   $72.1478   $72.15   $72.15   $72.10  
  Purchase #5 $104.54   13.540%   $118.6947   $118.69   $118.70   $118.70  
  Purchase #6 $216.54   8.725%   $235.4331   $235.43   $235.45   $235.40  
  Purchase #7 $216.55   10.159%   $238.5493   $238.55   $238.55   $238.50  
  7 purchase totals = $949.07       $1,053.7563   $1,053.75   $1,053.75   $1,053.60