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 $67.26   3.722%   $69.7634   $69.76   $69.75   $69.80  
  Purchase #2 $114.93   6.580%   $122.4924   $122.49   $122.50   $122.50  
  Purchase #3 $244.75   9.521%   $268.0526   $268.05   $268.05   $268.10  
  Purchase #4 $198.57   4.294%   $207.0966   $207.10   $207.10   $207.10  
  Purchase #5 $145.40   8.412%   $157.631   $157.63   $157.65   $157.60  
  Purchase #6 $170.67   4.324%   $178.0498   $178.05   $178.05   $178.00  
  Purchase #7 $234.31   10.418%   $258.7204   $258.72   $258.70   $258.70  
  7 purchase totals = $1,175.89       $1,261.8062   $1,261.80   $1,261.80   $1,261.80