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 $23.69   10.596%   $26.2002   $26.20   $26.20   $26.20  
  Purchase #2 $90.84   4.657%   $95.0704   $95.07   $95.05   $95.10  
  Purchase #3 $149.98   12.792%   $169.1654   $169.17   $169.15   $169.20  
  Purchase #4 $63.68   10.840%   $70.5829   $70.58   $70.60   $70.60  
  Purchase #5 $186.28   10.615%   $206.0536   $206.05   $206.05   $206.10  
  Purchase #6 $201.28   12.595%   $226.6312   $226.63   $226.65   $226.60  
  Purchase #7 $120.75   9.804%   $132.5883   $132.59   $132.60   $132.60  
  7 purchase totals = $836.50       $926.2920   $926.29   $926.30   $926.40