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 $147.53   6.254%   $156.7565   $156.76   $156.75   $156.80  
  Purchase #2 $208.89   13.219%   $236.5032   $236.50   $236.50   $236.50  
  Purchase #3 $204.91   4.488%   $214.1064   $214.11   $214.10   $214.10  
  Purchase #4 $120.35   4.291%   $125.5142   $125.51   $125.50   $125.50  
  Purchase #5 $149.31   5.396%   $157.3668   $157.37   $157.35   $157.40  
  Purchase #6 $57.45   8.433%   $62.2948   $62.29   $62.30   $62.30  
  Purchase #7 $242.77   5.324%   $255.6951   $255.70   $255.70   $255.70  
  7 purchase totals = $1,131.21       $1,208.2370   $1,208.24   $1,208.20   $1,208.30