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 $211.41   5.176%   $222.3526   $222.35   $222.35   $222.40  
  Purchase #2 $232.78   12.368%   $261.5702   $261.57   $261.55   $261.60  
  Purchase #3 $75.41   13.112%   $85.2978   $85.30   $85.30   $85.30  
  Purchase #4 $250.31   10.534%   $276.6777   $276.68   $276.70   $276.70  
  Purchase #5 $155.40   9.211%   $169.7139   $169.71   $169.70   $169.70  
  Purchase #6 $5.74   8.173%   $6.2091   $6.21   $6.20   $6.20  
  Purchase #7 $143.54   7.771%   $154.6945   $154.69   $154.70   $154.70  
  7 purchase totals = $1,074.59       $1,176.5158   $1,176.51   $1,176.50   $1,176.60