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 $58.47   3.613%   $60.5825   $60.58   $60.60   $60.60  
  Purchase #2 $43.75   5.368%   $46.0985   $46.10   $46.10   $46.10  
  Purchase #3 $157.28   9.836%   $172.7501   $172.75   $172.75   $172.80  
  Purchase #4 $97.74   6.408%   $104.0032   $104.00   $104.00   $104.00  
  Purchase #5 $87.86   4.350%   $91.6819   $91.68   $91.70   $91.70  
  Purchase #6 $69.50   10.423%   $76.744   $76.74   $76.75   $76.70  
  Purchase #7 $185.77   11.522%   $207.1744   $207.17   $207.15   $207.20  
  7 purchase totals = $700.37       $759.0346   $759.02   $759.05   $759.10