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 $58.96   5.636%   $62.283   $62.28   $62.30   $62.30  
  Purchase #2 $8.53   7.264%   $9.1496   $9.15   $9.15   $9.10  
  Purchase #3 $93.94   10.177%   $103.5003   $103.50   $103.50   $103.50  
  Purchase #4 $142.96   5.779%   $151.2217   $151.22   $151.20   $151.20  
  Purchase #5 $152.56   7.733%   $164.3575   $164.36   $164.35   $164.40  
  Purchase #6 $101.83   3.794%   $105.6934   $105.69   $105.70   $105.70  
  Purchase #7 $230.30   13.783%   $262.0422   $262.04   $262.05   $262.00  
  7 purchase totals = $789.08       $858.2477   $858.24   $858.25   $858.20