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 $236.34   10.466%   $261.0753   $261.08   $261.10   $261.10  
  Purchase #2 $217.31   12.653%   $244.8062   $244.81   $244.80   $244.80  
  Purchase #3 $171.35   3.176%   $176.7921   $176.79   $176.80   $176.80  
  Purchase #4 $203.28   3.762%   $210.9274   $210.93   $210.95   $210.90  
  Purchase #5 $44.71   8.613%   $48.5609   $48.56   $48.55   $48.60  
  Purchase #6 $246.59   4.409%   $257.4622   $257.46   $257.45   $257.50  
  Purchase #7 $240.88   9.225%   $263.1012   $263.10   $263.10   $263.10  
  7 purchase totals = $1,360.46       $1,462.7253   $1,462.73   $1,462.75   $1,462.80