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 $194.49   11.493%   $216.8427   $216.84   $216.85   $216.80  
  Purchase #2 $218.34   9.715%   $239.5517   $239.55   $239.55   $239.60  
  Purchase #3 $97.60   3.604%   $101.1175   $101.12   $101.10   $101.10  
  Purchase #4 $165.91   12.320%   $186.3501   $186.35   $186.35   $186.40  
  Purchase #5 $190.90   13.508%   $216.6868   $216.69   $216.70   $216.70  
  Purchase #6 $214.86   11.630%   $239.8482   $239.85   $239.85   $239.80  
  Purchase #7 $143.34   13.411%   $162.5633   $162.56   $162.55   $162.60  
  7 purchase totals = $1,225.44       $1,362.9603   $1,362.96   $1,362.95   $1,363.00