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 $146.32   7.310%   $157.016   $157.02   $157.00   $157.00  
  Purchase #2 $133.58   9.391%   $146.1245   $146.12   $146.10   $146.10  
  Purchase #3 $137.68   3.709%   $142.7866   $142.79   $142.80   $142.80  
  Purchase #4 $187.68   5.771%   $198.511   $198.51   $198.50   $198.50  
  Purchase #5 $174.79   11.699%   $195.2387   $195.24   $195.25   $195.20  
  Purchase #6 $28.69   7.625%   $30.8776   $30.88   $30.90   $30.90  
  Purchase #7 $131.69   9.262%   $143.8871   $143.89   $143.90   $143.90  
  7 purchase totals = $940.43       $1,014.4415   $1,014.45   $1,014.45   $1,014.40