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 $125.81   4.685%   $131.7042   $131.70   $131.70   $131.70  
  Purchase #2 $191.91   9.223%   $209.6099   $209.61   $209.60   $209.60  
  Purchase #3 $65.75   11.333%   $73.2014   $73.20   $73.20   $73.20  
  Purchase #4 $137.44   12.321%   $154.374   $154.37   $154.35   $154.40  
  Purchase #5 $88.71   5.693%   $93.7603   $93.76   $93.75   $93.80  
  Purchase #6 $166.29   13.220%   $188.2735   $188.27   $188.25   $188.30  
  Purchase #7 $176.61   9.612%   $193.5858   $193.59   $193.60   $193.60  
  7 purchase totals = $952.52       $1,044.5091   $1,044.50   $1,044.45   $1,044.60