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 $65.96   8.582%   $71.6207   $71.62   $71.60   $71.60  
  Purchase #2 $244.28   12.843%   $275.6529   $275.65   $275.65   $275.70  
  Purchase #3 $99.33   5.389%   $104.6829   $104.68   $104.70   $104.70  
  Purchase #4 $68.37   10.645%   $75.648   $75.65   $75.65   $75.60  
  Purchase #5 $148.53   10.538%   $164.1821   $164.18   $164.20   $164.20  
  Purchase #6 $239.83   9.863%   $263.4844   $263.48   $263.50   $263.50  
  Purchase #7 $185.93   12.522%   $209.2122   $209.21   $209.20   $209.20  
  7 purchase totals = $1,052.23       $1,164.4832   $1,164.47   $1,164.50   $1,164.50