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 $179.38   9.131%   $195.7592   $195.76   $195.75   $195.80  
  Purchase #2 $232.31   9.725%   $254.9021   $254.90   $254.90   $254.90  
  Purchase #3 $245.90   8.478%   $266.7474   $266.75   $266.75   $266.70  
  Purchase #4 $239.62   4.361%   $250.0698   $250.07   $250.05   $250.10  
  Purchase #5 $176.99   12.446%   $199.0182   $199.02   $199.00   $199.00  
  Purchase #6 $80.85   6.406%   $86.0293   $86.03   $86.05   $86.00  
  Purchase #7 $88.25   3.762%   $91.57   $91.57   $91.55   $91.60  
  7 purchase totals = $1,243.30       $1,344.0960   $1,344.10   $1,344.05   $1,344.10