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 $56.83   7.624%   $61.1627   $61.16   $61.15   $61.20  
  Purchase #2 $119.69   4.472%   $125.0425   $125.04   $125.05   $125.00  
  Purchase #3 $167.91   3.399%   $173.6173   $173.62   $173.60   $173.60  
  Purchase #4 $213.94   9.395%   $234.0397   $234.04   $234.05   $234.00  
  Purchase #5 $46.41   9.595%   $50.863   $50.86   $50.85   $50.90  
  Purchase #6 $14.29   12.262%   $16.0422   $16.04   $16.05   $16.00  
  Purchase #7 $116.91   7.356%   $125.5099   $125.51   $125.50   $125.50  
  7 purchase totals = $735.98       $786.2773   $786.27   $786.25   $786.20