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 $192.62   11.106%   $214.0124   $214.01   $214.00   $214.00  
  Purchase #2 $198.36   13.451%   $225.0414   $225.04   $225.05   $225.00  
  Purchase #3 $113.78   7.782%   $122.6344   $122.63   $122.65   $122.60  
  Purchase #4 $202.44   7.117%   $216.8477   $216.85   $216.85   $216.80  
  Purchase #5 $66.79   7.859%   $72.039   $72.04   $72.05   $72.00  
  Purchase #6 $51.78   4.182%   $53.9454   $53.95   $53.95   $53.90  
  Purchase #7 $245.39   5.370%   $258.5674   $258.57   $258.55   $258.60  
  7 purchase totals = $1,071.16       $1,163.0877   $1,163.09   $1,163.10   $1,162.90