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 $179.67   9.140%   $196.0918   $196.09   $196.10   $196.10  
  Purchase #2 $115.74   12.870%   $130.6357   $130.64   $130.65   $130.60  
  Purchase #3 $78.79   9.230%   $86.0623   $86.06   $86.05   $86.10  
  Purchase #4 $143.45   6.439%   $152.6867   $152.69   $152.70   $152.70  
  Purchase #5 $211.42   4.823%   $221.6168   $221.62   $221.60   $221.60  
  Purchase #6 $69.73   8.778%   $75.8509   $75.85   $75.85   $75.90  
  Purchase #7 $185.38   10.489%   $204.8245   $204.82   $204.80   $204.80  
  7 purchase totals = $984.18       $1,067.7687   $1,067.77   $1,067.75   $1,067.80