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 $58.95   3.643%   $61.0975   $61.10   $61.10   $61.10  
  Purchase #2 $41.43   6.788%   $44.2423   $44.24   $44.25   $44.20  
  Purchase #3 $25.85   12.870%   $29.1769   $29.18   $29.20   $29.20  
  Purchase #4 $242.82   8.816%   $264.227   $264.23   $264.25   $264.20  
  Purchase #5 $15.26   12.427%   $17.1564   $17.16   $17.15   $17.20  
  Purchase #6 $175.74   10.509%   $194.2085   $194.21   $194.20   $194.20  
  Purchase #7 $108.63   3.170%   $112.0736   $112.07   $112.05   $112.10  
  7 purchase totals = $668.68       $722.1822   $722.19   $722.20   $722.20