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 $91.76   4.193%   $95.6075   $95.61   $95.60   $95.60  
  Purchase #2 $156.35   4.216%   $162.9417   $162.94   $162.95   $162.90  
  Purchase #3 $38.48   6.723%   $41.067   $41.07   $41.05   $41.10  
  Purchase #4 $248.88   4.402%   $259.8357   $259.84   $259.85   $259.80  
  Purchase #5 $223.86   3.203%   $231.0302   $231.03   $231.05   $231.00  
  Purchase #6 $205.80   12.782%   $232.1054   $232.11   $232.10   $232.10  
  Purchase #7 $42.94   5.401%   $45.2592   $45.26   $45.25   $45.30  
  7 purchase totals = $1,008.07       $1,067.8467   $1,067.86   $1,067.85   $1,067.80