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 $176.25   11.218%   $196.0217   $196.02   $196.00   $196.00  
  Purchase #2 $233.78   11.718%   $261.1743   $261.17   $261.15   $261.20  
  Purchase #3 $209.54   4.164%   $218.2652   $218.27   $218.25   $218.30  
  Purchase #4 $172.63   4.121%   $179.7441   $179.74   $179.75   $179.70  
  Purchase #5 $109.51   12.444%   $123.1374   $123.14   $123.15   $123.10  
  Purchase #6 $129.88   4.247%   $135.396   $135.40   $135.40   $135.40  
  Purchase #7 $223.65   9.115%   $244.0357   $244.04   $244.05   $244.00  
  7 purchase totals = $1,255.24       $1,357.7744   $1,357.78   $1,357.75   $1,357.70