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 $164.66   6.112%   $174.724   $174.72   $174.70   $174.70  
  Purchase #2 $95.45   10.294%   $105.2756   $105.28   $105.30   $105.30  
  Purchase #3 $83.72   13.522%   $95.0406   $95.04   $95.05   $95.00  
  Purchase #4 $220.81   6.492%   $235.145   $235.15   $235.15   $235.10  
  Purchase #5 $142.51   13.688%   $162.0168   $162.02   $162.00   $162.00  
  Purchase #6 $179.99   9.585%   $197.242   $197.24   $197.25   $197.20  
  Purchase #7 $42.67   11.811%   $47.7098   $47.71   $47.70   $47.70  
  7 purchase totals = $929.81       $1,017.1538   $1,017.16   $1,017.15   $1,017.00