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 $211.46   9.756%   $232.09   $232.09   $232.10   $232.10  
  Purchase #2 $82.99   10.350%   $91.5795   $91.58   $91.60   $91.60  
  Purchase #3 $200.74   6.437%   $213.6616   $213.66   $213.65   $213.70  
  Purchase #4 $232.79   12.133%   $261.0344   $261.03   $261.05   $261.00  
  Purchase #5 $109.81   6.556%   $117.0091   $117.01   $117.00   $117.00  
  Purchase #6 $178.66   13.712%   $203.1579   $203.16   $203.15   $203.20  
  Purchase #7 $79.98   6.316%   $85.0315   $85.03   $85.05   $85.00  
  7 purchase totals = $1,096.43       $1,203.5640   $1,203.56   $1,203.60   $1,203.60