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 $68.31   8.700%   $74.253   $74.25   $74.25   $74.30  
  Purchase #2 $247.96   5.264%   $261.0126   $261.01   $261.00   $261.00  
  Purchase #3 $201.84   3.119%   $208.1354   $208.14   $208.15   $208.10  
  Purchase #4 $75.62   9.676%   $82.937   $82.94   $82.95   $82.90  
  Purchase #5 $172.66   11.196%   $191.991   $191.99   $192.00   $192.00  
  Purchase #6 $97.99   7.616%   $105.4529   $105.45   $105.45   $105.50  
  Purchase #7 $157.58   4.569%   $164.7798   $164.78   $164.80   $164.80  
  7 purchase totals = $1,021.96       $1,088.5617   $1,088.56   $1,088.60   $1,088.60