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 $183.40   6.676%   $195.6438   $195.64   $195.65   $195.60  
  Purchase #2 $112.39   8.286%   $121.7026   $121.70   $121.70   $121.70  
  Purchase #3 $245.86   9.517%   $269.2585   $269.26   $269.25   $269.30  
  Purchase #4 $127.37   9.430%   $139.381   $139.38   $139.40   $139.40  
  Purchase #5 $166.79   10.525%   $184.3446   $184.34   $184.35   $184.30  
  Purchase #6 $142.49   10.303%   $157.1707   $157.17   $157.15   $157.20  
  Purchase #7 $6.72   12.215%   $7.5408   $7.54   $7.55   $7.50  
  7 purchase totals = $985.02       $1,075.0420   $1,075.03   $1,075.05   $1,075.00