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 $177.76   4.680%   $186.0792   $186.08   $186.10   $186.10  
  Purchase #2 $54.51   8.439%   $59.1101   $59.11   $59.10   $59.10  
  Purchase #3 $169.91   8.757%   $184.789   $184.79   $184.80   $184.80  
  Purchase #4 $248.53   5.668%   $262.6167   $262.62   $262.60   $262.60  
  Purchase #5 $176.45   3.686%   $182.9539   $182.95   $182.95   $183.00  
  Purchase #6 $32.31   10.266%   $35.6269   $35.63   $35.65   $35.60  
  Purchase #7 $168.64   8.338%   $182.7012   $182.70   $182.70   $182.70  
  7 purchase totals = $1,028.11       $1,093.8770   $1,093.88   $1,093.90   $1,093.90