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 $56.36   11.230%   $62.6892   $62.69   $62.70   $62.70  
  Purchase #2 $26.31   6.542%   $28.0312   $28.03   $28.05   $28.00  
  Purchase #3 $152.41   12.550%   $171.5375   $171.54   $171.55   $171.50  
  Purchase #4 $226.46   9.779%   $248.6055   $248.61   $248.60   $248.60  
  Purchase #5 $205.46   9.217%   $224.3972   $224.40   $224.40   $224.40  
  Purchase #6 $171.54   4.625%   $179.4737   $179.47   $179.45   $179.50  
  Purchase #7 $154.48   5.855%   $163.5248   $163.52   $163.50   $163.50  
  7 purchase totals = $993.02       $1,078.2591   $1,078.26   $1,078.25   $1,078.20