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 $84.93   11.714%   $94.8787   $94.88   $94.90   $94.90  
  Purchase #2 $206.61   11.680%   $230.742   $230.74   $230.75   $230.70  
  Purchase #3 $188.65   8.751%   $205.1588   $205.16   $205.15   $205.20  
  Purchase #4 $183.73   10.329%   $202.7075   $202.71   $202.70   $202.70  
  Purchase #5 $95.64   9.197%   $104.436   $104.44   $104.45   $104.40  
  Purchase #6 $156.47   8.104%   $169.1503   $169.15   $169.15   $169.20  
  Purchase #7 $53.50   12.476%   $60.1747   $60.17   $60.15   $60.20  
  7 purchase totals = $969.53       $1,067.2480   $1,067.25   $1,067.25   $1,067.30