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 $188.79   3.672%   $195.7224   $195.72   $195.70   $195.70  
  Purchase #2 $177.50   8.839%   $193.1892   $193.19   $193.20   $193.20  
  Purchase #3 $148.49   9.724%   $162.9292   $162.93   $162.95   $162.90  
  Purchase #4 $121.31   3.839%   $125.9671   $125.97   $125.95   $126.00  
  Purchase #5 $65.38   6.783%   $69.8147   $69.81   $69.80   $69.80  
  Purchase #6 $230.35   3.254%   $237.8456   $237.85   $237.85   $237.80  
  Purchase #7 $168.99   9.300%   $184.7061   $184.71   $184.70   $184.70  
  7 purchase totals = $1,100.81       $1,170.1743   $1,170.18   $1,170.15   $1,170.10