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 $61.98   5.376%   $65.312   $65.31   $65.30   $65.30  
  Purchase #2 $235.34   3.549%   $243.6922   $243.69   $243.70   $243.70  
  Purchase #3 $155.25   4.293%   $161.9149   $161.91   $161.90   $161.90  
  Purchase #4 $231.92   7.617%   $249.5853   $249.59   $249.60   $249.60  
  Purchase #5 $104.51   10.419%   $115.3989   $115.40   $115.40   $115.40  
  Purchase #6 $17.34   6.397%   $18.4492   $18.45   $18.45   $18.40  
  Purchase #7 $177.82   11.516%   $198.2978   $198.30   $198.30   $198.30  
  7 purchase totals = $984.16       $1,052.6503   $1,052.65   $1,052.65   $1,052.60