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 $208.75   13.829%   $237.618   $237.62   $237.60   $237.60  
  Purchase #2 $155.58   13.767%   $176.9987   $177.00   $177.00   $177.00  
  Purchase #3 $18.43   5.314%   $19.4094   $19.41   $19.40   $19.40  
  Purchase #4 $92.99   5.393%   $98.005   $98.01   $98.00   $98.00  
  Purchase #5 $65.67   7.754%   $70.7621   $70.76   $70.75   $70.80  
  Purchase #6 $98.45   7.202%   $105.5404   $105.54   $105.55   $105.50  
  Purchase #7 $202.74   7.191%   $217.319   $217.32   $217.30   $217.30  
  7 purchase totals = $842.61       $925.6526   $925.66   $925.60   $925.60