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 $193.33   10.483%   $213.5968   $213.60   $213.60   $213.60  
  Purchase #2 $27.72   4.733%   $29.032   $29.03   $29.05   $29.00  
  Purchase #3 $44.93   4.666%   $47.0264   $47.03   $47.05   $47.00  
  Purchase #4 $219.62   7.677%   $236.4802   $236.48   $236.50   $236.50  
  Purchase #5 $186.40   5.232%   $196.1524   $196.15   $196.15   $196.20  
  Purchase #6 $183.27   10.234%   $202.0259   $202.03   $202.05   $202.00  
  Purchase #7 $164.29   8.715%   $178.6079   $178.61   $178.60   $178.60  
  7 purchase totals = $1,019.56       $1,102.9216   $1,102.93   $1,103.00   $1,102.90