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 $114.76   10.299%   $126.5791   $126.58   $126.60   $126.60  
  Purchase #2 $153.63   12.843%   $173.3607   $173.36   $173.35   $173.40  
  Purchase #3 $119.68   3.477%   $123.8413   $123.84   $123.85   $123.80  
  Purchase #4 $203.34   4.842%   $213.1857   $213.19   $213.20   $213.20  
  Purchase #5 $155.25   9.617%   $170.1804   $170.18   $170.20   $170.20  
  Purchase #6 $65.95   8.794%   $71.7496   $71.75   $71.75   $71.70  
  Purchase #7 $188.57   4.346%   $196.7653   $196.77   $196.75   $196.80  
  7 purchase totals = $1,001.18       $1,075.6621   $1,075.67   $1,075.70   $1,075.70