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 $69.37   7.409%   $74.5096   $74.51   $74.50   $74.50  
  Purchase #2 $106.64   9.801%   $117.0918   $117.09   $117.10   $117.10  
  Purchase #3 $79.75   6.429%   $84.8771   $84.88   $84.90   $84.90  
  Purchase #4 $189.81   12.244%   $213.0503   $213.05   $213.05   $213.10  
  Purchase #5 $224.74   10.385%   $248.0792   $248.08   $248.10   $248.10  
  Purchase #6 $117.88   8.497%   $127.8963   $127.90   $127.90   $127.90  
  Purchase #7 $71.90   9.307%   $78.5917   $78.59   $78.60   $78.60  
  7 purchase totals = $860.09       $944.0960   $944.10   $944.15   $944.20