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 $89.61   6.800%   $95.7035   $95.70   $95.70   $95.70  
  Purchase #2 $211.84   8.792%   $230.465   $230.47   $230.45   $230.50  
  Purchase #3 $16.65   5.470%   $17.5608   $17.56   $17.55   $17.60  
  Purchase #4 $178.68   11.623%   $199.448   $199.45   $199.45   $199.40  
  Purchase #5 $236.28   12.845%   $266.6302   $266.63   $266.65   $266.60  
  Purchase #6 $215.88   4.473%   $225.5363   $225.54   $225.55   $225.50  
  Purchase #7 $38.81   4.559%   $40.5793   $40.58   $40.60   $40.60  
  7 purchase totals = $987.75       $1,075.9231   $1,075.93   $1,075.95   $1,075.90