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 $208.64   11.792%   $233.2428   $233.24   $233.25   $233.20  
  Purchase #2 $13.63   3.789%   $14.1464   $14.15   $14.15   $14.10  
  Purchase #3 $99.86   13.746%   $113.5868   $113.59   $113.60   $113.60  
  Purchase #4 $185.91   3.846%   $193.0601   $193.06   $193.05   $193.10  
  Purchase #5 $74.36   3.611%   $77.0451   $77.05   $77.05   $77.00  
  Purchase #6 $236.73   11.844%   $264.7683   $264.77   $264.75   $264.80  
  Purchase #7 $64.81   3.104%   $66.8217   $66.82   $66.80   $66.80  
  7 purchase totals = $883.94       $962.6712   $962.68   $962.65   $962.60