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 $60.54   3.435%   $62.6195   $62.62   $62.60   $62.60  
  Purchase #2 $231.69   12.323%   $260.2412   $260.24   $260.25   $260.20  
  Purchase #3 $248.89   3.289%   $257.076   $257.08   $257.10   $257.10  
  Purchase #4 $222.53   8.169%   $240.7085   $240.71   $240.70   $240.70  
  Purchase #5 $144.30   13.186%   $163.3274   $163.33   $163.35   $163.30  
  Purchase #6 $161.29   13.717%   $183.4141   $183.41   $183.40   $183.40  
  Purchase #7 $46.62   4.232%   $48.593   $48.59   $48.60   $48.60  
  7 purchase totals = $1,115.86       $1,215.9797   $1,215.98   $1,216.00   $1,215.90