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 $92.88   5.664%   $98.1407   $98.14   $98.15   $98.10  
  Purchase #2 $206.88   10.716%   $229.0493   $229.05   $229.05   $229.00  
  Purchase #3 $189.73   9.720%   $208.1718   $208.17   $208.15   $208.20  
  Purchase #4 $54.70   12.845%   $61.7262   $61.73   $61.75   $61.70  
  Purchase #5 $144.94   13.702%   $164.7997   $164.80   $164.80   $164.80  
  Purchase #6 $105.78   11.706%   $118.1626   $118.16   $118.15   $118.20  
  Purchase #7 $99.90   5.265%   $105.1597   $105.16   $105.15   $105.20  
  7 purchase totals = $894.81       $985.2100   $985.21   $985.20   $985.20